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Television Repair Answered Questions

Public TV repear.



QUESTION NO. P715-5:  I have a CTC187BD RCA chassis.  I resoldered all connections for intermittent picture, now the picture is too wide and looks like pincushion problem on side.  Any ideas?
Problem may be the pin diode and associated capacitor. Also, I have seen the solder on the pin and damper diodes so poor that they physically fell out of the pcb.


QUESTION NO. P630-4: I have a Color T.V.25" Sanyo Model DS-25330. It burns R007(5.6 ohm 1watt)and horizontal output after 20 minutes of use. Any ideas?
Suspect flyback and any of the derived supply ckts. Also, make sure the replacement HOT is correct. Also, if the b+ goes to high the unit may shut down or could destroy the HOT. I'd suspect something in the horiz deflection/HV ckts.


QUESTION NO. P71-8: Does anyone know what causes vertical jitter on a Philco P2510RW101 (chassis 25S102)? I have seen this problem on a couple of Magnavox, and Sylvania TV's also but was never able to figure it out.
If it is accompanied with occasional audio distortion and colour loss suspect the AFT adjustment. If only on a cable source, and specific station, suspect clipped sync level from that specific source. Check the videl input to the jungle ic and the sync level & waveshap coming back out.


QUESTION NO. P71-7: I am working on a 25" RCA model G2628OTN chassis CTC157C. Upon powering up, the video is barely visable and the screen has white retrace lines from top to bottom. After a few seconds the little video that was visible is washed out with a white screen with retrace lines. The audio is fine. Also turning the set off and back on after it is warm, causes a delay of about 7 seconds for vertical deflection. Adjusting the screen control has very little effect if any. Is the problem in the video circuit or screen circuit or what?
Suspect the video output transistor. Very common on CTC169.
This is an answer to my own question. After further troubleshooting with the assistance of the Sam's photofact, I found the luminance buffer transistor Q901 to be leaky from collector to emmiter. I replaced it with an ECG159 and the picture is now fine.


QUESTION NO. P71-1: I have a 25" TV Sanyo Model DS-25230 after 20 minutes of use will go to shutdown. Any ideas?
Monitor the regulated B+ to assure that it does not go to hign, if the regulated supply is to hign all other voltages also increase, including HV resulting in protect circuit action. A failure in the hv protect can have the same effect.
Many of the heating problems I've run across are either components going into thermal runaway or bad solder joints. I've been using a jewelers loop magnifier to positively identify cracked solder joints which will give the symptom you just described. In conjunction with the magnifier, I've made it a point to identify the circuit giving me the problem by chilling it with cold spray. This works very well 99% of the time on heating and shutdown problems in TVs.


QUESTION NO. P623-2: I have a Zenith SS1937 with a vertical linearity problem. The set originally had a blown HOT. With a new HOT, the picture squeezes in from top to bottom.
Check the caps in the vert circuit and power supply with an ESR Meter. Probably one or more has seen better days. If all else fails, order the circuit module using the 9-XXXX-XX numbers found on the tag.


QUESTION NO. P629-4: RCA CTC169 B,35 INCH, repaired pin cush. problem and shorted HOT, now set comes on with vertical line, no horizontal. All secondary supplies are good ?
Recheck all you work around the horiz circuit and pcc circuit, I will bet you find a solder joint that you missed. Or did you forget to plug the horiz yoke leads back into the yoke plug?


RCA Model No. CTC175C suffered Lightning damage.
Replace Fuse,Low Voltage diodes, Q4103 & Q4105 5 volt regulator and 3 lead 12volt regulator. The 12 volt regulator may test ok Change it anyway.


QUESTION NO. P64-7: A Panasonic CT27G22 has about 1/4" white line at top of screen when the picture is black. I need to increase the height. How do I enter Service Mode? So far, I can activate self-test with the Power and Action buttons.
Short TP8 to gnd, FA-1 to FA-2. A yellow CHK should appear on the screen. Press Action & Volume UP at front of tv. Characters should change to red indicating that you are now in service mode. Power button on remote selects adjustments, B, sub-adjustments, C, CRT adjustments, D, geometry adjustments, and S, factory only setup. Channel buttons on remote select feature, volume buttons on remote change parametre value. To exit press Action and Power for about 2 seconds. TV sill switch off then back on tuned to ch #3. Changing the data in geometry mode will express changes in raster.


QUESTION NO. P623-5: I have an RCA (Dimensia) Model FPR2723E-1, Chassis CTC140E. The unit works fine most of the time, but occasionally will power off completely (no picture, no sound) without warning. The set will instantly come back on by itself. This may happen repeatedly for a couple of times then work fine for an extended period. A second unit, same model and chassis has also exhibited the same symptom at various times. Any suggestions on what may be the cause?
Remove sub-power board from main chassis. Resolder all diodes and pins on sub-power board, reinstall into chassis. Many times the solder breaks loose from the diodes where they are soldered to this small pcb.
Desolder the low voltage sip board (in front of the switching transformer) resolder all diodes, coils & caps.


Information for adjusting some manufacturer's TVs via digital service modes are addressed in the june, 98 issue of Electronics Servicing & Technology. The article is not comprehensive but does give information for NAP, Zenith, RCA, Sharp, & MECA [Quasar/Panasonic] televisions.


QUESTION NO. P618-2: I have a CTC 146L that is blowing the 1 amp. B+ fuse. The H.O.T. is good and the power supply is OK. I have checked the diodes and capacitors in the derived power supply circuits and have found no trouble. When I remove drive to the HOT by opening the base circuit, it does not blow fuses. I have checked caps in the horizontal circuit and found no trouble. Now I am suspecting the flyback. Is there some check that I can make to verify that before replacing it.
A ringing device or commercial flyback checker will give you a yes/no answer. Does the fbt become very warm when the transistor does blow out?? If it dows there is a high probability the transformer is defective.


QUESTION NO. P618-4: I have a Sony KV-27SXR10 Television which exhibits intermitent loss of luminence. The picture will turn dark red after a few minutes of operation and can be returned to normal by striking the set. This solution has recently lost its effectivness for the owner. Hence, a faulty solder join is suspected
Look for broken solder connections at the regulator ics mounted on the centre aluminum heat sink, towards the front of the chassis. Common problem.


QUESTION NO. P617-9: I have a Hitachi 31" TV with intermittant power problems. It will power up to about 5 minutes after it is powered off. Sometime maybe 50 clicks.
Check caps in horiz. drive circuit( most likely 100uf/50 volt).


QUESTION NO. P65-6: CTC146 has no vertical, just line. Replaced U4501, C4501, CR4501. 24V good and checked tuner solder joints. Any Help?
Check the vertical B+ resistors(10 ohm I think) Also check the diodes for the 12 volt run. Had one instance of front control pcb being "Windexed" and two corroded buttons was freezing the system control.


QUESTION NO. P69-8: I am working on a Mitsubishi Model CS-2653R with a lose of vert out. IC401 has the following readings 23v pin 7,0.1v pin 6, 0.09v pin5, 0.01v pin4 with a 6.5 mvac sig.,22v pin 3, 2.0v pin 2. Is the lack of an input on pin 5 appear to be the cause or ic401 itself?
Suspect the IC, however, if you scoped the drive and found no signal from the previous stage then there are other problems. Most of the problems have been defective ics and supply related as well as dried our caps.


QUESTION NO. P617-2: I am working on a toshiba 27in mod cx2668 with dead chassis no blown fuses. Low voltage supply checks good .Jumped the relay and high voltage comes up with green screen and no audio,also no user controls. Any tips would be helpful.
Probable failure in standby power supply or source to mpu and associated circuits. Probable open fuse device to standy supply or defective regulator ic.
If this has a switching power supply, check for a 100uf/10volt cap on the hot side of the standby transformer, and I think, C805 220uf/50 volt cap on the secondary(-30volt filter for the "earom". If it does not, check for a 100uf/160 volt filter in the standby circuit.


QUESTION NO. P610-5: How do you enter the service mode on Sharp TV model 21R-SC ?
Hold volume up and channel up buttons in while plugging set into to power. Tv comes up then in service mode. channel up/down selects register volume up/down selects parametre's value. Register numbers have an 'S' preceeding them, data will be expressed in hex code. See June's issue of 'Electronics Service & Technology' Magazine or Sharp service material.


QUESTION NO. P526-10: I have a video problem with a Sanyo 28" Color. Model 82C952U (Canada).This set is distributed by Sears Canada Problem: Intermittant video,with slight vertical compression top and bottom,only when video problem is present.OSD ok.I suspect a component(capacitive or resistive)around IC101 (LA7655N).I have not been able to isolate this problem with cold spray or heat. Any suggestions? Model may also be listed as 14231.
Does the supply voltages to the ic change with the presence of video?? Scope the drive signal with no signal and with standard video input.


QUESTION NO. P68-9: I am working on a sony kv-2162m9 tv. It works fine for about 30 sec, then the horizontal transitor or d613 blows. Just before crashing there is a arcing sound from the power supply area.Could it be the PS transformer - t602? I have ruled out the yoke and H.V. transformer.
Arcing sound from power supply destroying the Horiz output? Suspect the flyback, crt, crt socket, and other hv related components. Excessive current is destroying the Horiz output. This is being caused by the arc you hear. The voltage in the B+ power supply in normally not high enough to cause an arc.


QUESTION NO. P610-2: I have 2-KV-27V55 (chassis SCC-F84H-A) in for repair. After replacing Q601, Q602 & r607, they failed again in less than a minute. Horiz out x-sist is ok. Can someone would share their troubleshooting procedure for this power supply?
First, use Sony original transistors for the choppers. Also, check for a thermistor in the secondary of the supply that ocasionally fails. Generally. replacing the two transistors and fuse resistor with original parts normally sufices. Once in a while the thermistor also causes a problem along with a leaky diode in the secondary. We have been repairing these sets in the field for some time with apx 98% completion rate. For troubleshooting, the use of generic transistors is fine but we always put Sony components into the sets before returning to service.


QUESTION NO. P64-2: I have an Emerson model TC2555D which no longer responds properly to the remote, or to the buttons on machine. Most noticeably, both the remote and the machine's power button mute the tv instead of turning it off. However, this is not the same muted state as triggered by the mute button, because the screen does not display the word "MUTE" in green. The mute button still produces the expected message, but many of the other controls no longer perform as they had.
Sticking buttons or defective MPU IC.


QUESTION NO. P64-1: Does the Toshiba Cinema Series 32" TV have a "Raster Rotation" (or equivalently named) adjustment from its service menu?


QUESTION NO. P61-3: Toshiba CF2666R, chassis TAC 9102, circa 1991. I have a good pix, but the top four inches of raster has vert. retrace lines and Closed Caption data showing. The blanking bar is not visible, though. Sometimes foldover is visible, but not usually. Would this still be considered foldover? Caps in the vertical or the whole IC?
Suspect the electolytic caps in the vertical deflection and supply. Check with an ESR meter or, if one is not avail, subsitute the caps.


QUESTION NO. P54-1: I need a fly back number for a Sharp(model #19LP56).
The listed part # is RTRNF1445CEZZ. This crosses to most after market manufacturers.


QUESTION NO. P58-6: Does anyone know the values of RX3433 and RX3434 on a Zenith 9-1333-1 module.Model# SLS2549S?
Zenith 9-1335 which is very similar shows RX3433 as 15 ohms 1/2w and RX3434 as43 ohms 1w.


QUESTION NO. P528-8: Magnavox TV, Chassis # 25G1. Switched Mode power supply will not put out over ~ 55 volts. Have two sets w/ same problem.
Had the same problem. turned out to be IC400 Part# 483513097006. This is the optic-isolater in the power supply.


QUESTION NO. P527-8: NEC model ct-2750 27" ctv. powers up fine with a good picture and sound. after approx. 5 minutes vertical jailbars appear in the raster and the raster begins to dim. within 1 minute the raster is dark.
Check if the video processor ic in inserted in a socket on the main pcb. If it is, remove the IC, unsolder and throw away the socket, resolder the IC directly to the pcb. Have seen many strange problens in NEC basause of poor connections between the IC and socket.


QUESTION NO. P58-9: How do you identify wether a CRT is good or bad?
Does it arc when HV is applied or glow a pretty blue colour? Does the elements arc within the neck of the tube when the neck is lightly tapped [necessary to have the set turned on]? Is the definition of data displayed very crisp without any trailing colour or smear? Does the tube require longer than a 60 seconds to show any display? General functional checks plus the use of a good crt checker can certify your worries.


QUESTION NO. P514-4: Working on a Samsung TV\VCR Combo Model MVR-2100 TV portion will not power up and gives out a constant capacitor charge "squeal" from the high voltage section. VCR powers and functions normally using
the RCA outputs.
P/S squeal indicates probable short in supplied circuits. Possible hv or audio problems. Deflection circuits take most current so check there first. Also check rectifiers and filters in ps specific to tv section.


QUESTION NO. P518-9: I have a Zenith SC3943W that will turn on but not turn off. It has to be unplugged to turn off. Suggestions?
Burnt contacts @ relay. Latching but not releasing due to remaninant voltage following attempted shut-down. Check relay contacts and diode paralleling coil.


QUESTION NO. P520-9: Sanyo DDS923019" COLOR TV has a vertical picture is 1/4 the normal size. After 10 minutes of operation the picture grows to fill the screen but it is distorted and there are small horizontal gaps. I have replace the virtical drive IC451 and Video Detector IC101. The problem is still there.
Check for dried electrolytic caps in the supply and actual deflection ckts. Also check for resistors that may have varied in value. Since it opens up during operation expect something that changes thermally or only with applied voltages.


QUESTION NO. P520-7: I have a Sharp TV model #25NV68(BK) that has no power. You can hear the relay click. Any one had this problem on a Sharp?
I have experienced a fair number of opens at transformers in the newer Sharp tvs. Standby more prevalant than driver and FBT but have seen all. Also, check the standy power supply for b+ when the relay is energized.


QUESTION NO. P514-6: Toshiba CF2655R, faint vertical retrace lines. I cannot get green bias down enough, blacks have greenish tint. Replaced a couple dozen electrolytic caps. Still retrace lines.
Check for burned bias resistors/pots or leaky green drive transistor on CRT board.


QUESTION NO. P514-9: How do I get into the service mode on a zenith se2795 system 3 didital set? I want to adjust greyscale.
Try pressing the menu button and hold until the menu disappears. Then, on the remote press 9,8,7,6 then enter.


QUESTION NO. P417-2: I have a Sony KV-2092 tv which intermittently loses the tuned station on some of its channel numbers. What should I suspect?
Check for bab solder on the IF Coils and also on the ground tabs around the IF circuit. You can also see the plugs that make the connection between the main and the IF Board.


QUESTION NO. P56-2: I am repairing a Samsung C11-6229T t.v. - No picture at all - suspect due to screen voltage (G2 from FBT) approx zero.
The CRT socket had arced inside and there was consequently a leakage to ground - forcing 'screen' voltage to near zero.


QUESTION NO. P54-6: A Zenith SSB796H brought in Dead, found (MOSFET) Qx3407 and a resistor off it's gate on the foil side of PCB burnt beyond recognition. Anyone have the values for the Mosfet and the resistor off it's gate?
Since there is obvious damage to the pcb, flash over, etc why don't you get a replacement module from Zenith and repair the set. Use the 9-XXXX-XX numbers found on the original, defective module to get the part number you need. Having such damage in the power supply probably means there is more damage further into the supply and associated circuits.


QUESTION NO. P416-9: I am currently facing a problem repairing Panasonic TC-21L10 CTV with the smps. The smps is working fine with no load connected but when the tv ckt is connect the smps o/p voltage drops to half what is required(12&24 normally). I have verified that there is no short in the rest of tv circuit and same thing happens even if I connect a 100ma load at o/p
Replace the main switching transistor 2sc4804a with the same thing. This problem of load might have occured due to power surge/lighiting. It is little diffucuilt to remove the heatsink from the transistor so be careful.


QUESTION NO. P415-9: I am working on a rca tx826tb tv that is dead. tf01 vert shutdown was shorted and rf01 and rf 13 was open. also pin 20 of ir01 is missing the standby voltage. is there a way to defeat this shut down circuit?
Lift one leg of dx01 and dx02 to defeat the xray protect shutdown mode.


QUESTION NO. P416-8: I am working on a Mitsubishi CS-3103C T.V. The set cannot receive channels 2-28. 29-63 (last cable channel) are all fine.
Check for brown resin glue on the foil side of the signal PCB....especially @ the band-switching IC (LA7911). If no glue..try replacing the LA7911. Last resort...replace the tuner itself.


QUESTION NO. P416-3: I am working on a Toshiba CF2750K, the vertical output IC (AN5521, IC301) shorted which blew the fusible resistor R327. I have replaced both of these and now have a picture, however, the picture is not centered, it has a 1/2 inch band accross the top and the channel number, etc. are right at the bottom of the screen. All voltages and waveforms feeding the vertical yoke look good. Any ideas?
On most older toshiba tv's there are 2 caps that always cause vertical problems: C301 & C305 both are 2.2uF/50V HIGH TEMP! and are usually RED in color.


QUESTION NO. P42-8: I have a Magnavox with a shorted HOT the no. CSD 1555 does anyone have any spec's on this part ? I can't seem to find out any info. on it. Set Mod. HD1906 C121 Chassis 19P615-ooAA.
I checked philips service manual for this unit and the HOT part # is 4835 130 47897 which crosses to an
ECG 2353 NPN horiz output with damper diode.


QUESTION NO. P415-10: Sony KV-32XBR35 - no power - blown F602, R623. Any advice?
Check both switching transistors in smps circuit, check horiz. output transistor. Normally the smps switches short and open the fusable resistor. Replacing them may get this unit operational, however, if the horizontal output also is shorted you may have a defect in the fbt or deflection circuits or derived supplies.


QUESTION NO. P47-9: I am working on a rca f35100st ctc169. I have replaced q4101 u4101,jw340,and r4001 because of the dead set problem. After replacing these parts the set comes on. after a few hours q4101,r4001 and u4101 are shorted or open. Can any body tell the what is causing these things to short?
I just had this one! Replace the parts you did before to get the set to come on again. Plug the set in and keep it in standby mode. Measure the base voltage on Q4101 (SMPS power transistor) and it should be about -0.2VDC. When you turn the set on, I found it dropped to about -1.2VDC (reference to ground). If it's more positive than this, or if the transistor is *forward* biased, it will run *very* hot. In this case, check for a 3.0V zener CR4122 and capacitor C4108. Change both of these and your problems should be solved. (don't bother testing the cap, just replace with a 105 degree cap). If the base voltages are normal, check the "snubber network" C4111, C4112, CR4105, and R4119. Also check solder on L4101. I would also change the 'lytics around U4101 (SMPS IC). When you're done, Q4101 should not be too hot to touch after running for several hours, although it does run very warm.


QUESTION NO. P42-9: I am trying to repair a Sony Model KV-1882AEB (chasiis SCC-573A-A) This set has a prgrammable tuner. It appears to program ok but once power is removed the tuner loses its programmed channels. I was under the impression that a battery held the memory after power was off, but can not find any battery on the schematic. I have a feeling the problem is a bad CX7959 Sony Memory chip. Can anyone give me some thoughts on this problem also need a current address/ telephone # for the Sony westcoast Parts center.
Yes. Your problem is most likely the memory ic cx7959. As for west coast distributor Sony has a service/training center in Costa Mesa Calif.I do not have the telephone number however I suggest calling 1-800-555-1212 directory assistance for an 800 Sony listing and go from there.


QUESTION NO. P46-9: Toshiba 27in tv hit by power surge cx2668 tac8812 replaced c840 and c841 and 5volt regulator trip relay have high voltage but can only get less than 3volts out of 5volt regulator L78M05. Any ideas?
Start by unsoldering the output pin of L78M05 from pad. If the 3v doesn't come up to 5v with no load then the regulator is bad. If the output leg does come up to 5v then you have excessive load on the regulator pulling it down to 3v. There is no easy way to locate the load except to resolder the output pin of 5v reg. and trace every branch the 5v goes to and one by one unsolder that branch or ic pin from trace and see if 5v comes up if not resolder and go to another branch.Soon you will locate the defect. My suspicion is that it will be a bad ic.


QUESTION NO. P47-8: I am working on a rca f35100st ctc169.i have replaced q4101 u4101,jw340,and r4001 because of the dead set problem.after replacing these parts the set comes on. after a few hours q4101,r4001 and u4101 are shorted or open can any body tell the what is causing these things to short.
Replace Q4101,U4101,R4001 again if bad. Then also check or replace CR4122 and R4110.


QUESTION NO. P42-7: I am working on a Toshiba, Model # DA1766m-01 which only displays a white "Vertical" line; Yes Vertical. I found Q7630 shorted and replaced it only to have the exact symptom. I have no schematics and suspect that a fusible resistor or another component may have opened when Q7630 shorted. Has anyone had this problem and if so could you help?
Check for an open cap, resistor, solder joint etc. in the yoke vertical circuit.


QUESTION NO. P41-5: Does anyone know how to get into the service mode of a Sony KV-T29MN81?
Check for a small hole on the back panel of your tv. Puch a non-conductive device thru that hole and press select switch to activate service mode.


QUESTION NO. P330-3: I have a Sony TV model # KV-32S25 which came in dead. I replaced Q601, Q602, R607, in power supply and Q502 (horizontal output). The set now powers on but has no high voltage, sound and tuner functions ok. The high voltage seems to pulse on for a few seconds then disappears.
HV Protect or B+ is going to high causing HV shutdown. Have you tried disconnecting the hv from the crt & seeing if shutdown occurs then? Carefully PLEASE! May even be a fault in FBT.


QUESTION NO. P41-9: I understand Craig Consumer Electronics is out of business. Does anyone know where tv parts may be obtained?
Locate the FCC data from the rear panel. Check the FCC mfgr data base to locate who the original supplier was. Then, hopefully they may be able to supply necessary parts if set is not to old. Many brand name suppliers used another marketing name to sell their products, i.e zenith/ admiral/ bell & howell, etc.


QUESTION NO. P42-6: I am working on toshiba 27 tv cx2668 set will not turn on, hit by power surge the 5volt regulator has only 3 volts coming out. I have replaced it and also c840 and c841. Any ideas why I cannot get the 5volt regulator ic back to 5volts.
Does the +5 reg run hot. Seems as if you may have excessive load on the 5 volt buss?? Hit by power surge it may have sustained unusual damage.


QUESTION NO. P42-2: Panasonic CTK 2042R(other models too)sam 2694.Out of focus for the first minutes, some times more.After that works ok.Checked crt,crt socket and board,solder connection of focus lead,flyback,res.and pin 3(abl)of fbt,c565-npcap.Were is the problem in these sets?
Possible humidity problem with crt socket or problem with source [FBT]. Have you used a HV probe to monitor the Focus and HV for the first few min when the set is first powered up?/ Also check the regulated B+. Slow warmup of the crt may also cause similar symptom.


QUESTION NO. P318-5: Need RCA part# or equiv. for t4100 Viper Transformer in 27" tv model f27100ak, ctc140 board location T4100.
RCA,GE,PROSCAN CTC-XXX all have chassis families for a given chassis. They are indicated by the letters following the chassis number. Since your question didn't have trailing letters on the chassis This answer assumes no letters. For CTC- 140 with no letters and all the following 140, 140AC,140AE,140B,140C,140E T4100 Vipur Output RCA part# 179723 the writing on top of transformer for this series should be 2847401-502(1) You can also see SAMS manual # 2608-2. If this reply doesn't satisfy your requirements then resubmit the question with the trailing letters of chassis and I will ll be glad to research it for you.


QUESTION NO. P323-1: Sylvania t.v. model rkj 178 wa02 powers up o.k. but will not tune to any channels. There is just static on screen and out of speaker.
Check r321 10 ohm 1/4 w resistor. It feeds the +13v to the tuner.


QUESTION NO. P326-10: I have a RCA chassis CTC175 with the three tic, dead set problem. I went to my distributor to buy the "Chipper Check"PC Interface box and software which will check for defective IC's on the bus line. I got the interface but was told that they could not give me the software unless I was an authorized service center. Is there another source for this software, or am I just stuck With a $100 pc interface that I cannot use? I have contacted Thompson and they tell me the same thing. Please help!
The servicer can purchase the software direct from TCE Publications, 10003 Bunsen Way, Louisville, KY 40299, Phone: 502 491-8110. If they encounter any problem or have any questions regarding "Chipper Check" they can call our Help line at 800 711-6913.

NOTE FROM WEBMASTER: There was an answer posted here that was contrary to the above information. The manager of the Chipper Checker at TCE contacted us and provided the above correction. We regret the mis-information that was submitted to us and posted here.

The "chippercheck" will not allow you to check i.c's on the buss of a ctc175 chassis. It is for tuner alignment only on this set.


QUESTION NO. P323-7: I am working on a Sony kv27ts32 q601, q602 pwr conv are shorted r607 and r644 are open. replaced same parts and transistors shorted and resistors opened. has anyone encounted this problem and its cause.
Use original SONY PARTS. Check the Horizontal Output Transistor, if shorted you may also need a flyback. Also check for defective parts in secondary of main smps.
I had the same thing happen on an XBR version. Turned ou to be a shorted primary for the standby transformer( small xformer just forward of the 2 transistors)


QUESTION NO. P324-9: Could you please tell me the ratings of the 2SD1555 horizontal output transistor(particularly V ebo)? Iam using NTE2331 in a Magnavox RX4476 AK06(25N101-00E) and base voltage as well as J-test4 voltage and regulators are ok. The transistor heats up to over 52 degrees celcius after about 15 minutes of operation. Also, what is the inductance value of the Philips 3620-0028-0015 horizontal linearity coil I measured about 21uH? Vertical and horizontal deflection yoke resistances are 7.4ohms and 1.4ohms respectively vs. the 7.8/1.8 listed in the schematic, but both appear to be unimpaired. When the horizontal yoke is out of line transistor heats up to an acceptable temperature, which leads me to beleive that the problem is isolated to the horizontal deflection coil or associated components. Could you offer any suggestions on how to remedy this situation?
2SD1555:: Vcbo=1500; Vceo=600; Ic=3.5A; Pc=50W;Icbo=~10ua@500Vcb; Hfe=~8; Basing BCE with [2-16E3a] type case. The overheating of this component may be caused by incorrect waveform from drive circuit or defects in the ringing capacitors &/or coils in the horiz deflection circuit. Don't rule out the flyback or components in the derived power circuits powered from the flyback.


QUESTION NO. P35-1: I have an older Sony tv mod# kv-1710 problem: 2-3 inches from the bottom of screen has lost its picture! Any specific capicitor I should be looking for? Could it also be another component?
KV-1710, if there is an ESR Meter available you may check all of the capacitors in the vertical, derived, and main ps. Not having access to an ESR Metre, and from the age of your tv, it may be to your advantage to replace each of the electrolytic capacitors in the said circuits, esp the vertical supply and deflection. Also, check the bias voltages on the active devices in the vertical circuits, some of the resistance values may also have changed or the transistors may become leaky. I.E conduct lower than design spec.


QUESTION NO. P318-10: I have an RCA 19" Chassis# CTC-175A. The set came in with no On Screen Graphics. I soldered the usual grounds under shield and replaced the EPROM, T-Chip, CPU. The voltages seem to be normal. Pin 8 on Eprom has nominal 5v. Pins 5 and 6 have around 3volts each. I even tried a second new EPROM.
Replacing and programming the E-Proms are two seperate things. Did you reprogram the data into the E-Prom or does the set still refuse to initialize? Assuming the data in the E-Prom is correct, suspect power supply & or deflection problems. I'v even found shorted dampers and components that were never corectly soldered to the pcb.


QUESTION NO. P318-8: 1989 Zenith 25" console w/Remote. Model SE2507N. No apparent Chassis NO. Set has five seperate modules. Main-module on floor(# 9-516) pwr-supply on right, tuner/Display interface on left, Video interface on plug of Pix tube. No-pix, no-hi volt. Has distorted sound, can control volume with remote, can change channels w/remote. All fuses good, no visual component failure. Help!
9-516 still avail from mfgr. Good place to start since it has most of the deflection & ps circuits. Check Horiz output for shorts, check B+ @ main filter caps & horiz driver collector. Make sure CRT is good before spending much time or parts on 89.


QUESTION NO. P318-7: I have a Zenith TV model SS6509G that was the victim of a power surge. R3296 was blown apart, unable to find a replacement part number.
Find the little white tag, order the 9-XXXX-XX part number, and replace the module. Who knows what else was fried from the power surge. Check quality of CRT also before going too far.


QUESTION NO. P318-6: Magnavox RJ8530AK03 Projection TV. The problem is with the convergence drifting slightly out of adjustment all the time. For the most part you can make adjustments from the On Screen Display but it changes over the course of a few hours. I also have to break out the pattern generator every few weeks to make more major adjustments. The convergence board has been replaced once and is still relatively new. Am I missing something here? Also, I can't find a manual for this TV. Can someone help me find the values for resistors R53,54,55 on the power module board.
Let's see, from the back there should be two boards @ the vertical panel. Right power, left deflection. A problem with changing voltage supplied from either to the dynamic convergence panel will cause drifting. I've had better luck in just replacing both the PS & Defl panels or at least trying them with good [new] subsitute modules. Expensive !!The print should still be avail from NAP but maybe only on fische, better than nothing. Also, if you haven't already check the condition of the coolant fluid in the chambers @ each crt. Probably needs changing to get rid of bacterial growth that will cloud the fluid [looks like floaters].


QUESTION NO. P318-1: I am working on a Emerson TV, model TC1365B suffix L. It is dead. I have checked Sam's and cannot find schematics for it. The 115 vac primary fuse is good and the 6 vdc regulator has nothing on it's input leg.
Check for B+ @ the large filter caps in the main power supply, if there then advance to the regulator [ic]. Check the horiz output for shorts. Advance logically from power to sweep circuits checking for probable shorted or open components. Check high wattage resistors in both main and derived supplies.


QUESTION NO. P317-4: I have a Zenith model SlS 25535 that has a no power condition. Main and lo power supply fuses good. rx3433 burned. No apparent cold solder jointsor other damage 9324 diode in area shorted- now replaced. What is value ofrx 3433? any ideas on no power(startup)?
Suggest checking the CRT. Some of the SL models have crt failures that also damage the main modules. Check the crt with a good module or better yet, with a crt checker. Specifically check for inter-element shorts.


QUESTION NO. P317-3: I am working on a Zenith SLS2555S - after about 20 minutes picture gets very dark with barely visible blue. Turn G2 control down and back up and its good for another 20 minutes. Focus Volts vary from 690(working) to 410 (dark). G2 @ 7kv (constant). Any idea if it's the tube or flyback?
Probably the fbt, suggest trying another known good module or a CRT checker if available. Tap lightly on crt neck while viewing pix. If brightness changes while taping on crt or if there are flashes in the picture or physically within the crt neck then you know what's causing the problem.


QUESTION NO. P310-9: Zenith Model SD2511, After customer replaced power supply brd, audio does not come up right away, takes several minutes like something is heating up. Audio into output chips looks good. Voltage on input pins is low as if the limiter is affecting it. Only the 7 volt source is low ( 6 volts ).
Suggest checking ALL CABLES for proper hookup. Also try another known good P/S board. Heafty estimate including new autio module [if still avail] and audio interface module, mts-stereo decoder. Highly recommend looking for something stupid, like wires pulled from connectors, reversed or crossed cables, some do look alike.


QUESTION NO. P211-3: I have a Magnavox model RJ5540 AK01 TV (27G1-01 chassis) that came in with C502 fried as a result of a HOT with a leaky base-emitter junction, I believe. Could someone please give me specs of this disk bypass capacitor?
Use a 1.5kv/471pF polyurethane disk cap & replace the HOT.


QUESTION NO. P36-1: RCA TV, model F35751MB CTC169BG5 Vertical High and corner words lose (PIN CUSHION PROBLEM). Do you have procedure for imput to eeprom configuration?
Change the Pin Damper diode and associated cap [ usually .056 ]. You will find the cap slightly swelled due to internal pressure. Common 169 problem. Don't worry about E-Prom data until you see 175+ chassis.


QUESTION NO. P35-9: I have a Sharp 19" television that someone has been into. There is a part missing and I do not have a schematic. The model is 19LP16 and the location of the part is SCR701.
Sams lists sveral originaql part numbers but they all cross to ecg5457.


QUESTION NO. P225-10: Having difficulty with Magnavox 27T1. Unit does not lock on channel immediately. Requires 3 or 4 searches then continues to tick after pic is on. Have replaced aft coil & S.A.W. filter. Aft coil has no effect on pic. Unit has taken a lightning surge.
Anything from the RF input to the processor chip. Blitz usually destroys items that are not usual failures so assume every component in signal selection and processing may have sustained damage. Usually just rocking the aft adjustment will allow proper lock but after lightning anything goes.


QUESTION NO. P225-6: I have a Zenith SE 5221W (1989). Sound, no image. The tube is cold. High voltage circuits are evidently working (noise). Without an electrical daigram do not know how to approach the repair. Any suggestions?
Cold CRT? I assume that you mean the filaments are not lite? Confirm that the HV is functioning with a neon [ne2h] bulb attached to a non-conductive rod or stick. The bulb will light when brought near the flyback core windings. Asuming the hv is operating then check the connections on the CRT board, filament leads, and the connections on the module. If all else fails order the 9-XXXX module fron\m Zenith and repair the set. Of course, the filaments in the CRT may be open but highly unlikely.


QUESTION NO. P220-8: I have an RCA (ctc177) with a kind of degauss problem. The bottom right and left of screen are not well. At first, the tv was not working and I resolved the problem by replacing the STK730-010 (u4101) regulator. Can you help me?
Is it possible the tube was jarred or bounced shaking the shadow mask?? Sounds as if you may want to try some spot magnets. All the purity & convergence adj are done by the magic ring around the neck. New tube time possible.


QUESTION NO. P224-7: Magnavox TV Model RP2786-B904, about 5 yrs old. Has significant vertical overscan problem, and I desire to adjust vertical size. I'm not in the TV business and don't have access to TV service menu codes in other manuals. FAQs tell me how to enter service menu, but I am presented with a large matrix of un-labeled codes ranging from A:0-28 to D:0-28, each with a hex adjustment value. Any help identifying the right one?
NAP in Greenville Tenn will gladly supply info to qualified service companies and technicians.


QUESTION NO. P224-3: I am working on a Toshiba 27" TV model # CF2666A with chassis # TAC 9100. The set has no vertical deflection with the picture squeezed to a thin line in the center of the screen. I feel the problem is in a bad cap on vertical height board but I am unable to locate which cap it is. Do you have any information as to the likely problem?
Suspect either the vert output ic or the supply sources to the ic from the sweep ps. The caps may result in foldover or distorted sweep but rarely cause total failure.


QUESTION NO. P23-7: TV Emerson Model M1375RA - No raster or sound. HOT no pulse but has DC Voltage 130V, DC from power (5V Reg.) good. No DC voltages from flyback. Startup problem? I cannot find signal that would get things going.
On several of these we have found IC301 bad. AN5156k.


QUESTION NO. P128-1: I am working on a Sylvania 26" set which exhibits the problem of the H.O.T shorting out after replacement. The set will run fine for a day or so. I have resoldered T501 the horizontal drive transformer. I am also using an NTE replacement for the H.O.T. Should I use only an original NAP part or do I have trouble else where?
Remove the horizontal drive transformer, sand its conections and then reinstall it. Tap on top. If this effects the horzontal then the top connections are bad. They do not solder very well and you must replace. The number is on top, Put 361xxx in front of number.


QUESTION NO. P216-9: I have an RCA 25" stereo tv, model F25652BL, chassis CTC187AB. The set is 4 years old. Initial problem - Picture pulled in from top & bottom, static in picture. Tapping or cycling power would sometimes clear up problem. Set finally quit. Replaced HOT, set worked for about a week, then symptoms returned, and then HOT went out again. Understand this is a common problem with RCA / GE sets, but have not found solution yet.
See look under Sci.Electronics.Repair Faq for RCA/GE CTC 175/176/177 and follow reccommended repairs. It is also probable you have by now blown the E-prom in the set. If all else fails take the set to an authorized RCA repair shop.


QUESTION NO. P29-7: Mitsubishi CS27200 has about 1" of information around edge of screen and black in the center.
Turn off the Closed-Caption mode thru the Video settings via remote. It is probably set to "TEXT 4". Using the remote control: press >video< button until "cc:text" appears, press >adjust< button until "cc:off" appears.


QUESTION NO. P114-1: I am working on a RCA CTC-149 that the Horizontal scan is about 4 inches to wide. All other circuits are working.
If there is a blue rectangular capacitor or grey off the collector of the H. O. transistor. Change it if it is bulged out on the side.


QUESTION NO. P29-4: I have a megatron t.v. model# ctv-1371(e) thats channels up constantly without the press of buttons. It has a i.c. chip in it that I believe controls the channel functions. It is a mn15287hy. I do not have any specs on it. can anyone tell me which pins control the channel up, or has anyone seen this problem before?
I would first look for any jammed push buttons on the front panel. This will cause a in-key command to the mpu. This may be caused by debris around the button or a failure of the actual switch. Check them with a meter to confirm function. Any low/high at the switch inputs to the mpu may be causing constant scan, shorted caps etc attached to the ic. Look for the oblivious rathen than comdeming the mpu. You should be able to trace the paths from the buttons to the pins of the mpu. A good magnifier may help.


QUESTION NO. P25-3: How do you change the colour settings on the Goldstar 1715SS? There are no pots. Presumably it is done with software. Is it likely to be available?
Assume you are asking about customer's settings and not tracking? With original remote and G/S access code found in tech manuals you may change tracking [bias, etc.]. Customer's settings via on-screen menu in picture settings.


QUESTION NO. P25-9: Zenith SF2507N - Pix is dark, narrow & short with vert foldover when powered-up. increasingthe consumer picture level causes pix to shrink & start to shut down. Also any program with a white background causes the same. The problem gets better as the unit warms-up indicating an electrolytic cap is involved. However, I do not speak Zenith very well. Any direction would help.
Find the little white tag on the main board. It will be 9-XXXX-XX. Order a new board from Zenith & replace the one you have. The joy of finding out what is wrong with the original pcb may be outweighed by the ability to complete the service with a RMA board from Zenith.


QUESTION NO. P22-11: Troubleshooting Toshiba 26" TV, Model # CF2665K. No Sound. Having difficulty locating fault. I cannot switch from 'SPKR OFF" to "SPKR ON". Don't have remote but, front panel controls include: SPKR, CATV, VID, Rest, FUNCT, VOL UP, VOL DN, CH UP, CH DN. I get SPKR OFF always whenever I press Spkr. Switch.
May be op error. Could be defect in mpu. Suggest getting original remote and try changing parameters then. The setings change on some Toshib sets when you access the function without pressing select buttons. However it is much easier with the proper remote. Have had many customers not able to stop 'demo' mode because of fact when change is accessed it may be comitted without manually selecting desired change. I.E. when you go to item in menu you actually make a change in it's setting. I know, clear as mud.


QUESTION NO. P24-7: I am working on a 27" RCA ctc169 chasis, model#f27188bt.The original problem was a dead set condition caused by a shorted cr4101.After replacing the diode the set powered up ok and the video was good except for overscanning in the horizontal.Both sides of the picture are cut off.I tried to adjust the horizontal width pot but it had no effect.Is there a service menu I must access to adjust paramiters in an e-prom like the ctc177 chassis?
ANSWER 1: Excessive width usually caused by shorted PCC Diode (use ECG577) & Yoke return cap...either .047uF/400v or .056uF/400V. (Square,blue or grey plastic case) This cap is next to the PCC diode & MUST be replaced at the same time.
ANSWER 2: Sounds as if the pin damper diode and associated capacitor aprobably damaged. Diode is physically located in front of horiz output. Cap is a .056uf or similar in value. Cap may appear slightly swelled. Common failure that can destroy hot transistor.


QUESTION NO. P126-10: I am tying to fix a Sony KV-C27TD that blew up by a thunder. Surprisingly no filter nor fuse destroyed on the F1 board. The Q602 and IC601 were off along with a track near R614. Unfortunately after replacing these plus all capacitors around IC601 and transformer T601 no AC is detected on the secondary of T601. There is 360VDC on C604 but pin 16 of the IC 601 has only 7.6VDC instead of 9.4VDC. Please give me clue !
After being blitzed only God knows for sure. Get a good schematic from Sony and check each component in the standby power supply circuit. This is the starting point!! Check for any high wattage [i.e. over 3 watt]components being blown open. Any of the capacitors in the supply could have had the interior pierced by high voltage spikes. The main problem with lightning & power surges is that they do damage to items that usually do not fail in normal operations. Not being cruel the sky is the limit, you may very well get the set operating to find out 3, 6, or 9 months from now other components failing because of the severe stress.


QUESTION NO. P128-3: I have a sony tv KV-19TR20. when cold has raster with no picture. works fine when hot.
Does the audio go away also? Possible the grounds within the tuner or possible poor solder connectiona around tuner/if or at regulators on board.


QUESTION NO. P129-2: I have a Sylvania Model # SPA 4756 which has some intermittent read smear usually on the face of an actor. Also I have noticed that during some sceans the CRT is very dark where others are near normal. I do have a Photo Fact for the set, but am not sure where to concentrate. I.E replace the signal processor or whatever or could the CRT be on its way out.
It is probable the crt has seen better days. Check it with a tester if available. Be sure to check G2 & G1 bias voltages before condemming crt totally.


QUESTION NO. P126-3: I have a Sharp TV model # 19RP59 that shows no color. The color osc show 3.58087 mhz, which is too high. The trim cap (c809)works out of circuit, but adjusting it in circuit caused no change in freq. I have replaced the crystal. Any ideas?
Check other components connected to the video processor ic. May need to change procesor ic. Confirm proper voltages at chip.


QUESTION NO. P127-4: I am working on a symphonic tv model 13tvcr MKII. I inadvertently moved the triads color adjustments on back of the picture tube (6of em) and now I can't get a decent picture back. when I try to adjust the color the focus gets bad and vice-versa. Is there a certain process or any special equipment I need to do this?
Assumption is that you have mis-aligned the convergence & purity ring magnets around the neck of the crt. Suggest going to libraty and getting a book on TV repair and atempt to realign those magnets per information in purity static convergence section or the books. Be advised, it may take a bit of time and develop your patience. Also you may try degaussing the tv before doing anything. You do not want any speakers or loose magnetic materials around the tv while doing these adjustments, i.e. other than those designed into the set.


QUESTION NO. P115-5: Philips TV,chassis #27c9-03 Problem: After 5min of warm-up, herringbone pattern in picture plus an intermittant jitter.I suspect IC 201.
Possibly thermal changes in SAW filter components. Try tweaking coils near SAW/IF. If no help you may try cooling coils and changing those thermally sensative.


QUESTION NO. P119-6: I am working on a JVC AV-2750S with no raster/audio (only thing I hear is the relay). The unit may have been A/C spiked. Can't get the sch. from OEM or Photofacts. Any suggestions on what I should look at first?
Check +9 volt regulator P/N BA17809T


QUESTION NO. P120-5: I have a Magnavox RR1933 W422 tv with a vertical deflection problem. It has a horizontal line across the screen. The audio is fine. I checked the supply voltage (24VDC) to the vertical deflection IC and it was fine. I also tried replacing the vertical deflection ic and checked capacitors nearby. The line is still there.
You did not state if the bias voltages were proper at the ic or not. Probable the source isnot getting to this ic. Also check continuity of yoke windings and circuit components from ic to yoke inclusive of caps and resistors.
I checked the vertical ic inputs on this unit. Replacing M52030ASP (4835-2098-8106) solved the problem. This ic is available from MAT Electronics for $3.95.


QUESTION NO. P119-1: Can someone please supply me with the pin out configuration and voltages of MPU IC on a Magnavox 25n1-01 chassis. I'm trying to fix a dead set and I need to check the data pulses and supply voltages.
Philips part # for CPU for 25N1 chassis is 4835 209 87551

pins 1,3-6 customer controls (color, tint, etc)

pin 2 volume control .o1-3.8 volts

pin 9 aft 2.5 volts, 3 with no signal

pins 10-13 key board input

10- 5 volts

11- .09 volts

12- 5 volts

13- 4.3 volts

pin 14 coin. i volt no sig, 4.3 with

pin 33 reset 5 volts

pin 37 clock .03 volts

pin 38 c-enable .03 volts

pin 39 scl .07 volts

pin 40 sda 5 volts

pin 19 power on/off .09 on

35 IR input

31-32 Xtal 2.6 volts high side


QUESTION NO. P17-3: I have a RCA VR250. When plugged in the red led for power comes on. the display does not illuminate. I replace three leaky electrolytic caps(2 740 mF and one 2200 mF). Unit still exhibits the same problem. Is the 15volt test point on the supply sufficient to declare the supply good ?
I had the same problem with a VR450. A shorted cap C874 1uf@50 volt. was the problem.


QUESTION NO. P116-9: How do you perform the tuner alignment procedure on a CTC 175a chassis? I had a bad eeprom (dead set) and I wasn't able to record any values. The only thing that is left to do is realign the tuner. Do I need a special alignment generator or what?


QUESTION NO. P114-7: I Have a Toshiba CF2010j with a vertical deflection problem. The bottom Half is black and the top half has some kind of linearity problem or foldover. I have replaced the signal processing and the output driver with no repair.
To repair this problem you must replace two red capacitors.One is located inside the shield for the deflection IC. The other is in the vert. output ckt.


QUESTION NO. P114-10: Zenith SLS2549S with single horizontal white line. Similar to q P325-3. Should I replace RX3209 or resolder my Vertical IC connections?
Yes, also chesk the diodes around the vertical output device and supply B+ to it. If that fails find the 9-XXXX number on the module and replace it as a complete unit.


QUESTION NO. P18-4: I have a Magnavox M# RG4550 AK02 C# 26C813. It will not come on at all. I am getting Power all over the main board. But when I push the power button nothing happens.
Check for voltage at the mpu ic. Check for osc function at mpu ic, check for data input and output at mpu ic. Check for voltage at power relay coil terminals. Check for data input from in-key presses and from remote reciever. Check for +5 v or +9v at remote reciever.


QUESTION NO. P16-8: I am working on a Sony KV1998R. All the channels that are programmed in to memory have been lost. I can manually tune in to the channels, but I cannot "surf" through the channels. I have tried adding them back in to memory but they just keep disappearing.
Possible defect in memory ic or loss of supply to same or mpu.


QUESTION NO. P16-5: Am working on a Phillips chassis 26C614 that is in a Montgomery Wards TV. My problem is that I have raster and sound but when I hook up cable or ant. there is no picture or audio. Also cannot program channels.
Probable bad tuner, mpu, or memory ic. Check all voltages at tuner assembly. Check for communication data to/from tuner. Check for data communication to/from mpu. Highly suspect tuner or bad connections, lack of data transfer.


QUESTION NO. P16-4: I am working on a 25" Zenith stereo color TV Model SMS2553S. The problem seems to be in the tuning of the set. None of the cable channels (nor the broadcast channels) are being tuned in on frequency. It seems that the set could use fine tuning adjustment! I have tried with the "Auto tuning" setting in both "fixed" and "search". There is no noticeable difference in the performance. However the TV works okay with the camcorder (both CH 3 & 4) and the Nintendo RF input. Any clues?
Find the little white tag on the signal board. Order the replacement module [ 9-XXXX ] from Zenith. Install part and cure problem. Trying to trouble-shoot usualy cost more tham replacement. Note: replacement modules have been running aproximately 80% reliable.


QUESTION NO. P17-4: I have an older Zenith model C5556G with what I believe to be possibly a bad CRT. The set will intermittently turn the entire screen red, then shut down and come back on at channel 2. Once, the set was down for a couple hours with a red screen and would not come back up. There is also noticable image shrinkage when there is a bright (white) background, and occasionally thin zigzag lines across the top and bottom 1/4 of the screen (also appears related to image brightness). Pincushion also appears drastically different at different image brightness levels.
Yup, Bite the bullet, you describe classic failure of a shorted crt, red gun.


QUESTION NO. P17-2: Recently an RCA Mod# p46101wk, Ch# ptk169pua, Shut down ( Dead). An examination of the main board came up with a blown 5 amp fuse, an open r1v (an ac surge res. 1.8 ohm, 15w), the chopper trans. (Q4101 a B+ reg. # SGS 461 ), the I.C. u101 was replaced also replaced.. After power was applied the set came up with sound and the normal high voltage crackel was noted as well indicating it was present but no picture, guns were black. No video drive or somthing?
You did not state if HV stayed or if shutdown. If HV remains problem may be in G2, G1 supply or filament supply too. If HV shutsdown suspect HV splitter, common failure, or possible one of the tubes shorting, disconnect each HV lead from splitter & try operations. Also when chopper is blown usually replace the ps controller ic and check the diodes in the controller circuit. Intermittant shutdown or intermittant startup can be caused by CR4116, the +15 v supply diode. If Hot transistor is shorted change the Pin damper and associated capacitor, usually a .056 ufd or close in value. If cap is bad it usually swells a bit.


QUESTION NO. P1219-4: I have a Mitsubishi CK2604R Color TV that has sound and picture, good Vertical, but the Horiz size pulls in from the left and right when picture is bright. My 28KV HV only measures 18KV and of coarse all other voltages are low. The HV never gets high enough to shut its self of, I have check about every diode and resistor in the Horz circuit, everything points to the Fly back! It, however does not get hot. No way to tell if one or more of the HV diodes in the flyback are bad.
Try to check the scan derived voltages of the FTB. Try reading the filter capacitor. Most of it is operated 60 to 80 percent of the total voltage. If it is low your FBT does not receive enough voltage or there is something wrong with your FBT. Try adjusting the B+ of your PS then try to measure it in the B+ of FBT. There is a fusible resistor in between or a coil try to check it if its almost the same or try using a capacitance tester and measure all the capacitors in the HV section and horiz section. If these do not fix it try replacing the horiz IC or transistor.


QUESTION NO. P15-9: I have an EMERSON tv model TC1365A which keeps detuning and tuning in the station that it is on. In other words it will not lock in the channel that you have selected. I have changed the tuner, and the IC TA8680N but it stills persists. I assume it maybe the m/pro TMP47C634N, but have had no luck locating a supplier.
You will have to find an Emerson parts source for that specific MPU, If you are going to order it also get the memory ic. Before going that far check the small capacitors connected to the MPU and memory ic and those near the tuner. You may find some of then may be leaky causng the tuning problem. This has turned up in some Toshiba tvs also.


QUESTION NO. P15-8: I am working on a Magnavox 25N1-01 and I cannot get any relay action. The unit is completely dead with no fuses blown(F400/F401). HO, Bridge rec. check good. I've already replaced c411 as it showed signs of failure. The owner of the tv said that it had been hit by lightning and that he had heard a loud pop.
Check the standby power sources. Check for fried leads (you did say blitzed~). Check for voltages @ MPU IC. Check for data input to MPU via inkey or remote. Check for status changes @ power output pin of MPU. Check for bias voltages at on/off driver transistor. Check for apx 12 or more volts at coil terminals of relay. Must have standby to even attempt relay keying. Standy +5, +12, etc.


QUESTION NO. P128-6: I have an RCA TV CTC-131M. Chopper replaced several times. Lasts 1 mo. to 1 yr.... Set is now in shutdown mode and replacing chopper no longer works. Power supply will not start up with Horiz. Out. transistor removed. Replacing chopper turnoff and horiz output transistors did not help. Output from chopper oscillator IC appears to be normal & standby power ok. When set was working 129V was ok.
There is a RCA goldenrod bullitin #CTV-11 that will give you the fix for this problem. If I remember correctly there are two cercumstances that will cause this problem. RCA Part #829220 will cure the problem if the fault is caused by momentary interuptions of the AC power occur.


QUESTION NO. P1223-4: I am working on an RCA CTC175 which has no blue . I have replaced the color Ic. The is no voltage on the base of the blue output transistor. Don't have schematic and I am having a hard time tracing. Any suggestion?
ANSWER 1: You say there is no ( 0 ) voltage at the base of the blue output. There could be some bias there unless the devices to the transistor are missing or broken or the pcb is physically broken. Even if the transistor were shorted b to e there would be some voltage there with reference to ground. I would remove the trensistor then check for voltages. If there no base voltages then look for other devices, damaged or broken pcb or open foils. Throwing parts at the set probably will not fix it without finding out why the missing bias is gone. Once this problem is solved I bet your blue returns.
ANSWER 2: Try switching the blue output with one of the other colors. If you still don't have the color blue then your problem is in the screen itself.
ANSWER3: You need to get an RCA manual. All adjustment are made via the hidden service menu. The 2 most common problems with the 175/176/177 are bad ground connections or the EEPROM. First you need to solder all grounds, including those under and around the tuner sheild. Check the adjustments for the blue background and drives next. If replacing the EEPROM becomes necessary, you need to record all of the present settings, before replacing. All tuner and I.F. setings are stored in the EEPROM also. Replacements are set with nominal values only.
Ref to ans #3, be careful. If you record the old settings and use those settings in the new eeprom, your problem may remain. The new eeproms factory settings need to be tweaked thru the service menu. ie., tuner allignments, horiz freq. vert. size , etc. It has been my experience that the eeproms fail due to corrupted data, not a failure of the chip itself. therefore, copying old eeprom data to the new eeprom will cause the trouble to remain if the eeprom is indeed the problem.


QUESTION NO. P1224-1: I have a Sanyo model AVM-2555 - 25 inch stereo color TV about 1 year old, The picture is perfect, but the sound is real fuzzy. With one exception. Channel 4's sound comes in perfectly in SAP mode. All other channels produce audio that is low in volume and distorted/static low crackling noise as if the speakers were blown. When using the external audio outputs and running them to a stereo amp, the same distorion is present. Any Ideas?
Sounds as if the audio MTS decoder circuit may be to blame. You did not say if audio from an external device inputed via avio was distorted. My guess it probably is not. I am not certian if the MTS is part of the tuner assembly on this model of if it is seperate.


QUESTION NO. P1216-4: I Am trying to fix a Magnavox 27" console model #25EM2824P, older TV about 1980, there is a single horizontal line in the middle of the screen, channels come in fine sound is good, any help ? The TV did this once before, it sat for about 3 months when it was turned on it worked for about a month then did the same thing, tried to let it sit again but the picture remained the single line this time.
Could be as simple as a bad solder on an electrolytic capacitor in the vertical circuit. If you move all the caps in vert circuit one-by-one and height changes, then this is your problem.


QUESTION NO. P1216-9: I have a Hitachi TS-3600 television, a quarter of there top screen is is not displayed any more. I believe one of the capacitors is not working any more. Am I correct? How do I check when its still on the circuit board.
Probably not. I've seen a Hitachi CT1912A with a similar problem. Turned out to be vert drive or output transistor - can't remember which. Check by hitting one at a time with freeze spray and check for any reaction in picture height. Not only is this the easiest check, but the transistor will test OK statically and will only exhibit slight crackling at the highest frequency if using an audio feeback oscillator transistor tester.


QUESTION NO. P1222-9: I am repairing a Sony KV27EXR20. When the power switch is pressed I can hear a relay 'click'. No display or audio.
ANSWER 1: Suggest checking the Horiz. output and audio output devices for probable shorts. Also look for probable solder cracks around any upright voltage regulator ics on the pcb. Check for the proper B+ voltages from the regulator, may also be the regulator ic.
ANSWER 2: Replace with original IC # STR-S6301**** DO NOT SUB TO STR-S6301A ****


QUESTION NO. P1222-3: I have a Magnovox TV Model RR1937 W122. When it is plugged in, it comes on with volume all the way up or nearly so. None of the buttons work, neither does the remote do anything. I cannot shut off the set, change channels, or change the volume. Checked test points for proper voltage, all OK. I think it might be the TMP47C634N-R402 IC, but I want to be relatively sure before changing it. Anything else to check first?
Suggest checking the data pins, clock pins, and bias pins on the MPU which you may have dome already. Pretty sure bet if the voltages to this ic check ok but you havn't data transfer. Also you may try another clock crystal. If the MPU is functioning there should be pulses at the clock and stobe pins and at the data lines when a command is requested (key press).


QUESTION NO. P1219-3: I have Quasar Model TP1920DW-1 Chasis ADC195 that does a half roll & flips with jitters. Have checked caps near vert ic & changed ic.
IC301 Sig processor AN5301NK.


QUESTION NO. P1125-8: I am working on a Phillips tv, multi-mode purchased in singapore model # 33FL1880/56r. The customer complained that the set was progressively harder to start ( on off sequences). the switching power supply is now dead. all the outputs are not shorted. the driver is not shorted.
have found that many electonic devices with your symptoms are due to faulty capacitors in the control stage of the SMPS. These caps are typically between 1uF and 100uF. Check/replace all of them.


QUESTION NO. P129-6: I have a Zenith 27" console, model #SM2726EZW (C10 chassis). An electrical surge took out the set. I replaced the main board(9-1408-01) ,but now when the set is turned on it will play a short time then fade to black. Is my problem likely the picture tube, or is there an eprom setup on the main board like in the RCA CTC 175-187 chassis's? Could someone help?
I would try another "new" circuit board before the crt. Have seen up to 20% failure in some of the "bew" zenith modules.


QUESTION NO. P1126-9: I have a zenith c-2 chassis which has audio. When I press power it goes into h-v shut down. Any suggestions?
Replace the entire module supplied by a Zenith Parts Distribrutor. The rebuilt modules are aproximately 80 % reliable so your chance of recieving a good one is pretty good.


QUESTION NO. P1111-1: Magnavox tv/vcr Model# cct192AT01 Switching power supply won't start. When we pull out the power supply fromthe tv. tv voltage is ok. Tv does not have a short inside. We tried connecting a lamp to the source voltage 130 volts the lamp lights up. When we unplug it and plug it back in the lamp does not light up.Power supply does not start.
I had a cct190 that smps came up and shuts down. Unpluging the connector to main board smps stayed on. I found ic602 6v reg at 3vdc, replaced to correct.


QUESTION NO. P1114-6: I am reparing an RCA F20539DG T.V. but this brand´s diagrams are hard to find in Mexico since the company started its sales activities recently. Is there any site where I can get service manuals for RCA products or a place to buy them?
Suggest looking at the Howard Sams Fotofact web site. Search by model and Chassis Numbers,[CTC-XXXX]including the letters following. Either that or a local distribrutor for Sams Fotofacts may be able to order item for ud. RCA in Indianapolis probably would supply the schematic to an authorized servicer.


QUESTION NO. P122-5: I have a NEC 25" tv/monitor model ct2501(a) with vertical foldover at the top of the screen, with retrace lines coming down 5 inches from the top of the screen. It is a filter problem but I do not know what area it is coming from.
It is probable that one of the filters in the vertical circuit has dried out. It is also possible that the output device could be bad.


QUESTION NO. P1124-8: I have an Emerson TV model MS198RA that will only display a green color on the screen (not a green colored picture). When I turn the TV on, maybe 1 out of 10 times the picture will be normal for about 1 minute, then it will change to a bright green with no picture. The audio continues working fine. The other 9 out of 10 times there is never a normal picture, only the green screen.
There is probably a short from the heater to the cathode in the CRT.


QUESTION NO. P1126-8: I have a Magnavox 27" TV RJ5540 AK01 (chassis 27G1-01) don't have a schematic yet. Relay clicks when power is depressed no pic or sound. R448 glows.I cannot read the value well. It looks like color code is brn-blk-grey-gold (1,000M 5% ?).
1 ohm, 1 watt. This resistor is protection for 130 B+. Better check your flyback and HO Transistor. Sams#2676


QUESTION NO. P1125-5: I have a 27" RCA TV model F27632SE chassis number CTC177BH2 the original problem was the picture drops down about 2 -3 inches, turning the power off and back on would sometimes correct this. After being bumped the volume display does not function properly it stays on the min. setting and cannot be adjusted with the remote or using the front panel (there is no sound). Also pressing the remote TV on a second time produces a black screen with" H3:60 PM FM 88.1 " displayed. Pressing channel + increases the FM stations by.2 until FM 107.9 then NWS A, NWS B and back to FM 88.1. Is this a bad Eprom?
Do all the poor solder repairs per RCA specifications. Order a new Eprom, hopefully you have an operational computer and software from RCA to reprogramme the Eprom. If not, enjoy reprogramming it from the service literature. Should repair your problem.


QUESTION NO. P1120-4: I have a 27" RCA TV model F27632SE chassis number CTC177BH2 the original problem was the picture drops down about 2 -3 inches, turning the power off and back on would sometimes correct this. After being bumped the volume display does not function properly it stays on the min. setting and cannot be adjusted with the remote or using the front panel (there is no sound). Also pressing the remote TV on a second time produces a black screen with" H3:60 PM FM 88.1 " displayed. Pressing channel + increases the FM stations by.2 until FM 107.9 then NWS A, NWS B and back to FM 88.1. Is this a bad Eprom?
First thing to do with a 175, 176, or 177 chassis is resolder the grounds on the shields for the tuner & microprocessor. Be sure to remove the bottom shielding on the tuner to get at the ground connections inside. This should fix picture height problem, possibly audio, snow, and intermittent power as well. As far as the EEPROM see P512-1. Immediately after plug-in the voltages may oscillate (set having problems) for a while on EEPROM. Check when they steady out after 10 secs or so.


QUESTION NO. P1114-2: I am looking for a list of valid parameters for the rca ctc 175c, chassis. The ones that I have from a different chassis are not working.
From what I've seen, parameters for a 175, 176 and 177 chassis are all about the same. At any rate the 3 security parameters are the same. Try varying the horizontal frequency to get a picture first & verify picture is "good" by going to next parameter (02) then adjust the rest. See for the details.


QUESTION NO. P1117-7: I have Zenith TV Model SLS2555S with Q3431 Blown apart. I am trying to get the schematic but supplier says it is not available. I would like to know if anyone has had this problem.
121-1264-01 is the part number of the transistor that is blown apart. Usually the regulator transistor str? is sometimes shorted also. This is probably either due to a power surge or lightning but the most likely cause is the picture tube starts arcing and blows the power supply.
I have seen a lot of tubes do this.
I have one in my shop too. These are the parts I replaced in the power suppy: ICJX3431 (STR53041), Resistor (rx3433), Resistor(rx3433), Q3431(NTE123ap).


QUESTION NO. P1118-7: Mag. 25d500 chassis, 93 model. has an aft problem similar to problems they have had with the saw filter. Have changed the saw filter, aft coil, and swapped the tuner. Works ok with a tuner snubber. Voltages at tuner seem to be ok. Anybody seen this?
The problem was the aft coil and someone had cranked on the rf agc control at another shop.


QUESTION NO. P1030-7: I have a Emerson EC133A that has no color the IC voltage and waveforms look great. Sometimes you can see a faint osc of color. I have changed the crystal and checked the capacitors around circuit.
I had a similar problem with a sony monitor. The problem was a false contact in the solder. So resolder all pins.


QUESTION NO. P1030-9: Sharp TV #25RV69/ Picture shrinks to small white line in the middle of screen. Tap the flyback or Hor. Yoke and picture jumps back for a few seconds. Anyone run into a similar problem or have any recommendations?
I have had the same problem and it was a intermittent vertical o/p ic, lightly tapping the heat sink will cause the vertical to collapse and return.


QUESTION NO. P1013-5: Mitsubishi CS-2701R. After replacing vertical amp la7838 vertical deflection was restored but will not adjust down to fit screen (excessive deflection).B+ voltages appear correct.
There is a 1ufd capacitor normally tantalum but in some cases a regular electrolytic beside the o/p that goes leaky.


QUESTION NO. P1016-11: I have an RCA CTC166CR which will not power on. The high voltage is OK. All voltages at the low voltage power supply are OK. No derived volts from flyback.When power switch is pushed indicator light comes on, flashes 3xs then goes out. H.O.T. ok. Could the problem be in start-up? Xtal is ok micro has power, reset ok. I have two of these tv's with same condition.
Ground pin 18 of u3101 see if hv comes up if not cr4103 is breaking down check on pulse at pin 18 of u3101 check colector voltage of q4161 if low (19v) replace c4605 measure r4163 should be 1.2k.


QUESTION NO. P1016-8: I have an RCA CTC177 that had the ususal bad ground under the tuner however this set also has narrow horiz width and picture is fine for a few minutes then pulsates goed to vert line the all snow as if the cable was unhooked (can't turn off when this occurs. Once I heard a arching noise just before turn on ofter plugged in.
Check r4517, r2709 off pin 4 of ihvt also cr4402,q4851 and pin 2 of l4853.


QUESTION NO. P1026-4: Working on RCA CTC 131-A. This set has the chopper power supply. Originally, set came in with shorted chopper. Replaced and set worked fine for about one week. (Also soldered base and emitter) Set returned with blown main fuse, and blown chopper. Replaced chopper. Set continues to blow fuse. Chopper is O.K. now. Replaced chopper cutoff (Q100). Still blowing fuse. (Checked C105, O.K.)
Ground tp 408 while ac is applied and see if set will come on. Also check CR301 for short I have also had R103 open intermittently.


QUESTION NO. P1021-3: I am working on a Mitsubishi (Electrohome in Canada Model 66CG01 which has no colour. Video is good, everything is good except for colour either on the main screen or PIP.
You have a problem on the pip board, may have a bad trimmer cap for 3.58 crystal on bottom left side looking from back or a bad feed through on the double sided cct board.


QUESTION NO. P1024-2: I am working on 27" RCA TV CTC140AJ that has an intermittant power problem, the set would for awhile and turn itself off but would come back on immediately, other times it would go into on & off mode constantly. I have checked to sheilds and resolder most connections also, checked for cracks on PCB.
Remove the sub-power board that houses the rectifier diodes. Resolder every connection and then reinstall the sub-power board.
iThe pwr on/off,volume, and other functions pass through the tuner module. Take the cover off the tuner and resolder all cracked or burned connections.


QUESTION NO. P925-1: I am working on a 10 year-old Mitsu 2654R set that has no vertical deflection, only a horizontal line, although the problem is intermittant (more often than not). When the problem does not manifest itself, the picture is "wavy" until the set warms up. I have cleaned the boards, but the problem still exists.
When not working check for vcc on vertical to see if vcc has dropped off or just dropped enough to cause this problem. Take the vertical trans. # & cross to ecg, find diagram of part, look for vcc on 2 places on chip or should be if it is a 12 to 14 pin vertical.


QUESTION NO. P929-3: I have a mitsubishi cs1942r with int. audio and video flickering. The tuning voltage drops out, but I cannot isolate trouble.
Check for brown glue on the main board & assoc. boards. This is a common problem. Remove all of the glue you can find.


QUESTION NO. P1010-9: I have an Emerson 25" TV model TS2581RD with a supply limiting 3W resistor, R251, burned up. What value is this resistor, the ink evaporated when it blew.
There doesn't seem to be a R251on that chassis. There is a R521,however, that fits your discription. It is 4.7 5% 3W and goes to pin 3 of IC501.


QUESTION NO. P1010-7: I am working on a Zenith SLS2553S 25" television. I seem to only have green and red. For about a day, the picture would eradically switch between all blue and a "normal" picture. Then it stopped turning blue and I was left with a very green looking picture. Any clues?
ANSWER 1: Check for ring cracks at the video output transistors on the video output pcb. Common problem.
ANSWER 2: Check for bad connections of the crt, but I think you'll find that the picture tube is bad, they've had alot of trouble with the tubes in those. Sometimes they will exchange even if barely out of warranty.


QUESTION NO. P106-13: I am working on a 1987 Sears color TV, on the inside it looks like a Toshiba. The problem is the tint control does not hold and when adjusting the tint it shifts about randomly. I've located the tint section on the board and was wondering if this inability to lock the tint might be caused by a leaky capacitor. I cannot get the schematic for this set (model no. 562.40320700) so if anyone has an idea what I should look for I would appreciate the help.
If ANY controls have not been rotated in a while they will exhibit these symptoms. Spray out w/cleaner/lubricant Chemtronics tun-o-power or the like to solve problem.


QUESTION NO. P930-3: I have a RCA PTV CTC 169BT retrace in all tubes can turn out with bias but then picture washed out pulses. flyback rings good ok no screen adj on flyback.
I sugggest checking G2 source, diodes, capacitors and connections to IVHT. The G2 being non-existant or to low may be your problem.


QUESTION NO. P930-5: I have a GE 27GT613 with the CTC177BE chassis that has had the usual grounds resoldered. All VHF channels (2-13) do not tune. Snow only. All UHF and
cable channels normal. The failure occured suddenly while Vhf was in operation.
It sounds as if the E-Prom may have given up. I suggest replacement and re-programing data into it. Also check answer for #P-723-1 for link to very good information RE:RCA/GE CTC-177 chassis & it's problems.


QUESTION NO P922-5: Sylvania TV RPF702AK01 Looking for value of R400 on main chassis board.
According to my schematic, R400 is a thermister Connected betwen the junction of D401,D402 &T402-4, rated at 16.1 cold. PN 483511637005


QUESTION NO. P926-5: Working on a Magnavox Tv chassis # 25N1-01. It had a bad flyback and HOT which I replaced. Now after a few days the Horiz out transistor blows. I put an STK brand in it . Do you need exact replacement transistor for this set? I am unable to locate the reason for the short.
Check horizontal driver transformer for poor solder connection. I have had no problem with ECG, NTE or SK HOT subs.


QUESTION NO. P912-6: I am servicing a GE TV model 13GP203 chassis TX81E and I changed all the damaged parts except one, which is a resistor, RP41, because it is burned and I can't see the value.
I believe the set in question is almost if not identical to RCA TX81F. If this is true, RP41 is 2.2K & connected to the emitter of TP10, the HOT & DX101 cathode.


QUESTION NO. P926-7: I have 3 different model Mitsubishi TV's in the shop with the same video or no video..sound is ok....models include :CS-27MX1,CS-2656R & CS-2725R. Has anyone had similiar problems with any of these units?
ANSWER 1: Inspect the chassis. Is there an upright pcb containing many surface mounted components? This is the pip module, C7001 leaks electrolyte and eats away the fine traces on the face of theboard. Replace the capacitor and repair the defective foil. This should cure your symptom.
ANSWER 2: I have seen a CS-2656R with the same problem after being hit 3 times by lightning via co-ax cable, I believe. I did the repair the last 2 times, and both times it was IC202 ( a 12 pin SIP dual video/audio electronic switch ). Scope pins 11 & 12 ( video in/out ) for complete TV signal, or alternately, jump them. If you get video then IC202 is bad. Crosses to ECG7066. Caution customer to disconnect co-ax when not in use! I also remember Mitsubishi tech assistance telling me to check an 8.5V? ZD, but can't remember which one.


QUESTION NO. P915-2: I am working on an Emerson model #TC2555D television that when you turn it on, you hear a click and then nothing happens. If you keep trying, eventually it will come on but only stay on for a few seconds. Each time you turn it on, it will stay on longer, until finally, it stays on. But when you turn it off, and let it sit, the process starts all over again. Also, when it does first come on, there is a green tint to the picture, any suggestions? I have replaced the horizontal output, just in case, but no help.
check electro. caps. in & around the power supply


QUESTION NO. P97-1: I am stumped! I am having a "vertical overlap" problem with a Toshiba CX28409 TV and have traced the problem down to the vertical output IC (AN5521). I have tried replacing this chip but when I do, the fusible resistor connected to the VCC blows and the chip becomes shorted out. I have tried several chips as well as the EXACT replacement from Toshiba but I get the same results. I put the original chip back into the circuit and I have my original overlap problem back. There seems to be a compatibility problem with the replacement chips but I can't for the life of me figure out what it is. One other note: these IC's have a large heat-sink attached which is mechanically (i.e. soldered) to ground.....could this somehow be the source of my problem?
Leaky cap, an electrolytic right next to the vert chip.


QUESTION NO. P910-9: Toshiba cf2667 has a black band at top of screen. When it is cold it is okay but after on a few minutes the bar comes on. It does not make picture smaller just has black at top 4 inches
Use cold spray to find the leaky cap probably electrolytic cap in vert circuit.


QUESTION NO. P912-1: Toshiba model CF2768 TV: After approx. 5 min. warmup, motorboating the in audio and dark bars flashing in the video at the same time; however, the raster seems to be okay. The distortion appears to come from the MTS module. Coolant spray has no effect.
Probable hair line cracks around the ground connections of the Tuner and MTS assemblies. May attempt repairs with very small iron. Otherwise replace. Both are common failures in Toshiba sets.


QUESTION NO. P98-1: Sony KV-2647R television is basically working after replacing a number of components i.e. H.O.T, Flyback, Caps etc., there is too much contrast in fact the whites are very white to washed out or out of focus. to correct the problem the picture control has to be adjusted to minimum with the sub contrast controll also at minimum. It seems that the dynamic picture IC cannot respond to scene changes. The 15.75 volt, 12.66v and 196v sources derived from the Flyback are low. 13.8 vs 15.75, 12.1 vs 12.66 191 vs 196 etc. I have no explanation for this, but I beleive this may have something to do with the dynamic white problem. The transistor, zener and resistors in the 15.75 regulator circuit are OK. Is it possible to have a Flyback Transformer which is not matched properly?
It is very possible that you have a crt with low emission. The washed out whites may be blooming. Check the crt before investing much more money or time. 26 " seemed to have a shorter crt life than the 19's and 27's.


QUESTION NO. P94-2: I am working on RCA Model F27100AK that has an intermittant power problem. When the set is turned on either by using the remote or pad the set turns itself on and off constantly. The power does not stay on long enough to see anything on the screen. I can hear a clicking sound as it turns itself on and off.
The clicking sound your heard was the degaussing relay, it opens to turn off the degaussing coil about 5 seconds after the unit is turn on. Listen for the HV cracking noise when the set is turn on to see if H. output is working. Also check those intermittent shield and EEPROM problems from FAQ.


QUESTION No. P87-2: Magnavox n25 tic tic. I found d445 but still bad. Any help out there?

First solution:I would try removing the vertical output IC,IC550. If this gets the set to power up,I recommend disabling the 27VDC scan derived circuit and use a regulated DC powersupply,preferably one with a current meter,to drive the vertical IC. This will save you time and money if there is another problem causing it to burn out the IC. I would also check the 121VDC regulated powersupply.If it is not being filtered like it should it could cause a spike voltage on the secondary windings of the flyback and will cause D445 to fail. If C411(100MFD 250VDC)changes value just the right amount it will not show up in the picture or raster like a regulator problem but it will show up if you scope pin 7 on the flyback. Second solution:If I remember right the set will tic if the Hor. Output Transistor is shorted.


QUESTION No. P821-8: I have a Sony KV-27EXR10 that came in dead replaced strs6031 now the set comes on but the B+ is only 100V all other voltages on the G board are also low ie the -22v is -15v and the 15v is 10v the B+ is supposed to be 135v. The ic does not appear to be running hot and cold checks on the components on the G board seem to be fine.

Check for defective 135v reference regulator IC SE-135N (TO220) optocoupler, 2SA1175 OVP-1 transistor and related circuits.


QUESTION NO. P826-8: Symphonic Mod#TVCR13D1TV has a luminance problem. The brightness is at high but picture is dark and flickering.
Check G2 voltage, if not stable, screen / focus divider on flyback is bad replace FBT, also check resistor in ABL circuit.


QUESTION NO. P828-11: I am working on an RCA TV CTC167C chassis. The problem is that there is no video, the display works but looks as though it is shrunk a little on top. Everything else works fine. Anyone had a problem like this before?
Problem caused by a shorted boost-trap capacitor in vertical output circuit. That is an electrolytic capacitor between cathode of pumpup diode and vertical B+). This would cause DC level to shift on vertical blanking signal and kill the video signal.


QUESTION NO. P828-3: I am working on a TH-33VS10 Panasonic T.V. (possibly the Japanese name). The picture is great except for a complete lack of red.
Check red cathode pin with an oscilloscope for proper signal average DC voltage on any CRT cathode should be about 150v if singal is present and voltage is correct, CRT is defective. Best still is to check with a CRT tester.
Have you ever tried switching drive signals at the point of entry into the CRT board? This will tell you a lot especially if you do not have a CRT restorer.


QUESTION NO. P93-4: Magnavox 31U1 with 1" triangle spot in center of screen at turn off. Spot remains for 15 minutes or until anode voltage of 25 to 30 kv is drained using hi-volt probe. The original problem was a defective tuner. I did not notice the spot before and thought I had created the problem. Checked possible bleed path of R539, R572, R573 off DAG line and C511. Also ground from chassis to CRT board.
The symptom you are describing is known as "AfterGlow" and is caused by the persistance of the rare earth phosphers. RCA has had this symptom for many years and assure technicians and customers this is visable evidence the crt is good quality. RCA would comment that the longer the afterglow persisted the better quality vacuum, tube quality and probable life expectancy. I have seen this symptom numerous times and have seen no determental effects from it other than kids circling it with crayons.


QUESTION NO. P828-1: I am going to pick up an Hitachi television model # CT4532 The television has a transformer problem (perhaps flyback) and I am trying to determine how much work I have ahead of me.
Unless you receive this set as a gift don't get too excited. Some of the components may not be available any longer from MFGR. Horiz drive and Flyback have been a source of service problems. Also regulator and convergence related failures. Over-all these sets were quite reliable however, as they age, as with all things, other things do and will happen. If you enjoy a challenge go ahead.


QUESTION No. P811-3: I have a Zenith model SS1937S9 television that has a problem with a picture that slowly fades to blue after it has been on for a while. It will gradually return to normal after a while, but some times it will stay blue until the set is turned off then back on again.

The problem is that you have a short in your blue gun inside your picture tube. It is a common problem with Zenith's.


QUESTION NO. P824-4: I have a SEARS LXI TV. Its about 7 years old. One of my kids hit some combination of keys on the remote and now a message scrolls continually thru the picture. This happened a couple of years ago and a repair person was able to give me the combination to turn the message off. I lost the combination. Can anyone out there help?
Try pushing the volume up and down buttons at once.


QUESTION No. P812-2: I have an RCA TV that has no color; chassis ctc157. I have replaced the ic1001 chip, xtal, resisters and caps in the circuit and still no color. When I inject 3.58, I have got color. Voltages all check good. Need some help on this one.

Replace C2812. Fairly common problem.


QUESTION No. P821-2: Toshiba Model CX2778 when plugged in the power relay clicks very fast. Jumpering contacts on relay for troubleshooting resulted in clicking, stopping after about twenty seconds and set runs fine once warm. I suspect negative voltage regulator STRD 1005. Has anyone come across this? I should also note it is not necessary to push the power button for relay clicking to start.

Toshiba CX2778 no power due to open cap 840 (330uF16V105 deg.). Also change C841, C822. Check for bad resistors, diodes, etches due to overheating.


QUESTION No. P89-3: I am currently working on a Zenith Sentry 3 Model H2013Y7 that powers up as soon as it is plugged in. I replaced IC 6000 but to no avail. I compared it to a working set of the same model and the only difference I noticed was a constant 5v on the input to the switching transistor for the power supply. When power is on the screen gets a raster that is green snow and cannot change channels.

I believe your set is in hotel mode. Get into the service Menu by continously pushing the menu button on the remote untill the menu goes away them push 9,8,7,6 enter. you will find a listing for hotel mode turn it off.
Once the service menu is activated by the menu, 9876 routine you should see a selection to set the auto power on. Many of these are plugged into the cable boxes and customers seem to prefer them to have the tvs come on when the cable box is turned on rather than using two power commands. Simply turn the auto power function off in the service menu.Being in the Hotel or private label mode seems to have no effect.


QUESTION No. P87-3: I have a Mitsubishi 27" late model with low volume from audio output on - via RCA jack - on back of unit. Need suggestions on how to adjust.

Most Mitsubishi TV's audio output RCA jacks are variable level controled by TV volume control, volume has to be turned pass midrange to have decent RCA output level but you can always turn off the speaker with speaker switch or speaker control on menu.


QUESTION No. P87-11: I have a TV GE model 27GT618 with chassis ctc187BD2 which has no pic or audio. I have all of the non flyback power supplies working, but the flyback derived supplies are dead. There is no drive to the hor out transistor. The drive should come from the t chip, but there is none. The EEPROM has a running clock/data, although I do not know if it is correct. At least it is not dead. Is there an easy way to isolate the problem? Can I somehow "jump start" the horizontal to bring up the other supplies?

You maybe able to jump start the tv by doubling the safety cap.


QUESTION No. P730-7: I am fixing a 27" Sony Trinitron with digital tuning (Model No. KV-2780R) which when the set is initially turned on, it seems as though the station is not tuned in properly. You see the tuned station, but with a bit of snow, and the sound is somewhat distorted.

I usually replace the tuner assembly rather than attempting repairs. Also the if/mts assembly may also have intermittant connections which can exhibit symptoms such as bad audio, snowy pix, intermittant breakup of pix, poor sync, etc. I have done quite a few of these and just order and replace the complete units.


QUESTION No. P726-2: I have an RCA CTC130 and color does not come in on ch 3 and 5. Any thoughts?

You did not state if you are using direct broadcast or cable hookup. First thing I would check is to substitute the tuner if available. Supply NTSC standard signals to the RF input and see if colour is present. If so suspect shifted frequency signals from CATV source. AFT circuit may be to tight to lock onto centre of channel allowing proper reception. Also, read section 12.1 of Sam Goldwasser's TV Repair FAQ at


QUESTION No. P725-5: This is a Zenith set came in without a mod.# (Label had been peeled off). It seems to be about 4-5 years old. At first no video with an on screen prompt that said "AC Line is failing" and then dead set.

Zenith TVs have part numbers for the modules affixed to the modules. There is a small white tag showing the part number. It will start with 9-XXXX-XX. Having that information will allow one to order replacement modules. Sounds as if the standby power supply and mpu may have sustained damage.


QUESTION No. P722-1: I am working on a RCA Model F20251WN with a CTC176F2 chassis. The unit does not power up when the power button is pushed. No power relay click but I read 130 volts near the switch mode regulator STK730-010 and 148 volts at the horizontal output transistor. I read voltages on it and 3 pins read 4.* volts.

Some time these set get off frequency so this works some times. Take the safe cap put another on top, this will let the thing power up. You will not hear the relay. Then turn power on and hold. Now push menu and push power on two or three time then push volume up. That should get you there. On most ctc chassis you have to resolder the the tuner grounds. This is the first thing to do. There is a code to get in to the memory of these sets.


QUESTION No. P723-1: I need to know the sequence of programming for the memory in a General Electric, model 27GT613 TV.

Refer to the article at look under TV and RCA/GE refer to the excellent description about the CTC177 and it's faults. Included is a guide to programming the E-Prom.


QUESTION No. P718-4: RCACTC177AF2/3 original problem was a grainy picture. I checked out the tuner and it had the cracks as usual. I resoldered the tuner, and micro shield, now I have no power. I replaced the eeprom with no luck using rca part# 218399. I have 165 coming off power supply. I have 149 volts at horizontal output transistor. I have checked the power switch and it is good. I have also replaced cap c7v a 200 volt 680uf that was reading 62 volts to ground. After replacing read 0 volts to ground. Same problem, no power up.

CTC-177 Check for a good tech writeup on this chassis and hints on many repairs. Also EST Mag July 97 issue has a very good article.


QUESTION No. P77-2: I have a JVC 27" color TV model AV-2751S. The verticle sweep quit. White horizontal line across the middle of the screen. What is the most likely cause?

Resolder cold solder joints on the vertical output ic.


QUESTION No. P77-11: RCA F27195CP Chassis CTC140 will not power up. The front panel or remote power switch causes high-pitched sound, then set turns off. Before, set would sometimes power off, but would come back on by itself, or after a while the power switch would turn it on.

Remove sub power board that contains the power supply diodes. Clean off old solder and resolder each diode and connecting pin. Reinstall sub power board. Also check for ring cracks arround IVHT and in area of IF SAW filter. Numerous intermittant power problems have been due to bad solder joints on the sub power pcb and cracks near the flyback.


QUESTION NO. P616-3: Toshiba TV model# CX2978C works fine when video is connected to the RCA inputs using a VCR to change channels. When connected to RF1 or RF2, no video, just snow with hiss for sound. Replaced tuner same problem.

These Voltages are close as to what I remember: AGC around 2.5V, BM 11.9 to 12.1V, IF 1.5 to 1.9V, CLOCK/DATA/ENABLE 0 to .1V P to P. There should be 30V and 5V if any voltages are low or missing desolder the tuner from the unit and trace voltages back.


QUESTION NO. P610-4: EMERSON TC1365B seems dead. Pressing power button causes relay to click. No H.V. H.O.T. checks good. I have replaced IC501 voltage regulator with no change.

Is there 165V on Hout Emitter? If not, trace from Hout back thru till you find Resistors,ect..(of course be using a variac). If there was 165V on Hout there are two possibilities: either No HDrive or VOut is shorted or no VOut Pulse.


QUESTION NO. P613-1: I have a GE Color TV (AB/AC Chassis) that has a perfect Black and White picture but NO color. So far I replaced the IC300 Color IC and that did not help. I did that because I saw no color signals at the 3 output pins of IC300. I hooked up a color bar generator for test purposes and see there is color signal getting to the input pin of IC300. I resoldered many griplets and that did not help either. Anyone have any further clues as what to look for? I suspect that the problem is somewhere near IC300.

Check r326, r322 and c328. Also instead of just soldering the griplets you may need to wire around them on the bottom side of the board.


QUESTION NO. P67-1: Samsung mod#TC2540S sometimes comes on with only about 4in. of height in the center of the screen.

I have found many problems with vertical compression or foldover to be due to bad higher voltage electrolytic caps (100v and up), typically 2.2uf to 10uf in the vertical output/drive circuit. They are often discoloured making them easy to spot. Also check for the usual, cold solder, power supply voltage to vertical stages. Yokes are rarely bad.


QUESTION No. P63-2: I have an rca chassis ctc130 it will be on for a few seconds and the picture shrinks up on one side and takes out the HOT. Flyback is Ok and so is Hoz. Yoke.

Replace hot emitter resistor with the exact value. All the HOT current passes thru this resistor


QUESTION NO. P67-6: I just fixed the power problem on an RCA console TV (model # GU795H) but now when I change channels it loses the vertical sync. If I adjust the vertical size down, the scrolling stops and I can change channels all day and everything is fine except now I have a shadowbox TV instead of a full screen TV. I can adjust the vertical size back to normal and everything is just fine again until I change the channel and then the process starts all over again.

Read section 9.5 of Sam Goldwasser's TV repair document, downloadable from this site.


QUESTION No. P520-1: Is anyone familiar with an RCA CTC 175 chassis that exhibits low audio output, even at maximum volume?

ANSWER 1: Perdon por no escribirte en tu idioma pero existen 2 soluciones pero el problema es causado por la EEPROM. 1a.- Solucion economica; Desconectar Colector de Q1903 (audio mute Transistor) no es lo correcto pero soluciona el bajo volumen y ademas trabaja el mute. 2a.- Reemplazar EEPROM; pero antes verifica la configuración que guarda, para que la vuelvas a grabarla, (solución Correcta).

ANSWER 2: Replace eeprom. Go into service mode and copy all the values first. Then install new eeprom. After starting set install your copied values into new eeprom. Do not remove anything from chassis and while you are at it resolder all the ground connections around micro sheild and under tuner shield.


QUESTION No. P512-1: I have an RCA CTC177 chassis. Power does not turn on. Pin #5 on U3101 should have 0V but it is 5V. Is this a bad U3101?

First check voltages on U3201 (EEPROM) pins 1,2,3,4,7, are ground, pins 5,6,8 should be about 4.8v, if not replace U3201. When replacing the EEPROM you will probably need to program it or else be sure to purchase one preprogrammed. If you need the parameters to program in look on a Sam's set 3221 or post a question here. RCA/GE Colour TV Chassis. From CTC-169 and above. Severe pincushion distortion or dead chassis. Stand by supplies may or may not be functional. Check horiz. output for short in dead chassis. Replace pincushion damper diode and associated capacitor. Usually a .056 or close in value. Also HOT if shorted. Symptom found in direct and rear projection chassis. Confirm desinated value of pincushion capacitor for proper value. Varies from chassis to chassis. Bad cap may appear swelled.


QUESTION No. P58-1: JVC AV2590 with vertical collapse. Replacement of C420 restored the full screen but I now have vertical rollover 3" at the top. I have checked and/or replaced caps in line to yoke with no results. Voltages appear normal. I can adjust screen on the flyback and set will nearly collapse.

Make sure you replace C420 with exact same value, also bridge caps. in vert. with same value, this is critical. Also check for and remove any glue that is used to hold components on copper side of pc board as this sometimes causes leakage between traces.


QUESTION No. P51-5: TV/VCR COMBO brand=MEMOREX model= 16-410 not turning on. The Low Voltage PS is not on. If the 5V load is disconnected, the LV PS comes up, but set cannot be turn on. 5V regulator and several caps had been replaced.

C1026 470uf 16 volt.


QUESTION No. P429-6: I have a sony kv-27xbr51 that reqires about 1/2 hour warmup before I get sound and audio. If I use my vcr as the input to the tv, I get picture immediately but still no sound.

ANSWER 1: I had a similar problem with a sony kv-20s10. I went through it by the numbers and got nowhere. finally I cleaned the main board (I use de-ionized H2O you can use any cleaner) this procedure "fixed" the problem. I haved fixed an NEC TV once this way before. With the proliferation of SMT and denser baords, dust will continue to be a growing problem. Clean those boards.

ANSWER 2: Resolder Ic581, IC582, HDT, & All heat-sinked components on P/S PCB. Also Check for Expanded caps
on P/S PCB

QUESTION No. P49-1: I am working on a Samsung 25 inch TV with vsible retrace lines at the top of the screen down to about an inch and a half.

Sounds like a vertical problem. Heat and chill vert. caps to get a reaction and locate the bad one. May even be the filter cap on the b+voltage for vert. from flyback, 22-28 volts.


QUESTION No. P418-3: Magnavox VRU222AT21. Very late model with what looks like a Funai chassis. Exhibits no operation whatsoever. At plugin, red power l.e.d. comes on and stays on. Checked power supply voltages and all check low. Static check of power supply components proved negative. Chassis OK.

C1026 470uf 16volt. Many companies use this Funai type chassis combo tv/vcr. If this cap is on the 5-6 volt standby supply, try it.


QUESTION No. P417-2: RCA CTC130A had shorted horiz. output transistor. When replaced output wave form is 1300 volts p-p when it should be 910 volts p-p.

ANSWER 1: Replace horz. output emitter resistor with exact value. It is too small a value (.27) commonly, to accurately check. Also may have an open retrace cap off C. of h.o.t.

ANSWER 2: Last one of those I fixed had the horz. freq. so far out of range that set was in shutdown mode. To check if this is the case, install a 2200pfd(.oo22) 1600 volt cap across the horz. retrace cap C4402. this will bring down the high voltage enough to show a picture. the horz will be way off freq. so enter service mode and adjust value to 11


QUESTION No. P43-3: I have a Hitachi Model #CT4535D Chassis # VP9X1 with HOT shorting out. The problem seems to be intermittent because the set will operate fine for hours up to as long 8 days turn it off and on each day. But then one day it will just begin to lose convergence and then cycle sometimes once or twice and then shut down the deflection and high voltage section. Unplug it and plug it back in and sometimes it will stay for a time. Then I can remove the convergence output board and it will operate fine (except for convergence of course). When the problem occurs it always starts out with poor or even no convergence.

First check for bad solder on convergence output IC's. sounds like a thermal problem you can find with Freeze spray on the convergence board. On the bright side a new convergence board will probably fix your problem.


QUESTION No. P416-5: Magnavox 13L4-04 chassis. Replaced FB 2A fuse and 130v regulator. Pix and audio are fine when slowly increasing AC level up to 110vac, but increasing beyond 110vac, set shuts down and relay clicks continuously. R502 checks good.

If 130 v not high check 200v while raising variac if 200v goes high change c505 and/or c506 . IF 130v is going high check reg. components off pin 2and c432


QUESTION No. P325-2: I have a Sony 27 inch television model kv-27exr25. The switching IC strs6301 burned out and was changed by a strs6301A. All the voltages come to normal in the board G but the strs6301A burn after 15 minutes or so.Does anyone knows if the strs601A is the equivalent?. I have not been able to find any other bad component in board G.It is working at about 50 kHz. Does any anyone knows where to find the specifications for the strs601 and the strs6301A?

You might want to try the original Sony part pn#874992081. The normal operating temperature for this IC is 175-F. Check with a temperature probe.


QUESTION No. P47-7: I have a Toshiba CF2668B television with a vertical linearity problem. The picture is cut off on the bottom and stretched out on the top. I have changed or checked all of the electrolytic capacitors and resistors in the vertical circuit. There is no adjustment for linearity. There is an adjustment for vertical height.

Change C301 by the signal processing IC. The value is critical. I have also had C305 and the vertical output IC cause same symptom.


QUESTION No. P42-6: I have a Mitsubishi 27" PIP T.V. Model number CS27MX1 that when I turn it on I get red and blue lines across the sreen for approximately 30sec and then the screen goes black. I still have sound.

ON mit 27ex lines then black w/audio the problem was caps 7001-7014- and 7036 on 7000 PIP board.


QUESTION No. P318-5: I have a customer that is complaining that the info banner on stations such as CNN is cut off on both sides of the screen. Can someone tell me if the horizontal width is controlled by a pot or setup menu in a Zenith SM2745MK8 TV? If its a pot what is the number.

R3249 is the horizontal size control, located near the corner of the board by the vertical size control.


QUESTION No. P325-3: I have a Zenith Sentry 2 model # SLS2555S with a line in the middle of the screen.

Replace RX3209 with a 1 ohm 1/2 watt fusible resistor i.e Zenith p/n 63-10565


QUESTION No. P32-7: I have a Toshiba model CF2628 TV in the shop that intermittently has the picture go dark with retrace lines visible. Also, when it does this the video appears to be "negative". I can simulate the same condition by moving a setup switch that is located on the CRT driver board. I thought this switch was the problem and jumpered it for testing but the problem still intermittently exists.

Solder all the pins of P902 and P903 on the CRT board, even if they look OK. That should fix that problem.


QUESTION No. P220-3: NEI 28" Nicam Stereo Television C28F1FXN circa 1995. No picture - all other functions perfect. CRT board heater voltage reading at 13Volts AC relative to adjacent ground connection, nearby 200V DC connection fed by same ribbon cable is ok. No visible dry joints, heaters glow but not very brightly. As far as I can see LOPTX provides output to CRT board heaters. ADDITIONAL SYMPTOMS RECEIVED ON 3/1/97: When the LOPTX screen output is increased, a dark blue line across the middle of the raster is observed - looks a little like field collapse. Suspecting colour decoding chip. NB I think the heaters are ok after all.

The set has no picture due to the fact that the field oscillator is not running. This sends a feedback to the colour IC making it shut off the tube drive to protect the screen from burn much like a screen saver on a p.c. I would investigate the field output circuit. You should have around 20v on the field output ic if not check the suplies for an o.c feed resistor etc. If you do have the supply I would change the chip.


QUESTION No. P32-3: RCA vr664hf. After plug-in, unit will take up to 20 mins. to become fully operational.

Check or replace the 22uf 50v capacitor on the primary side of ps. Also the 80uf 200v cap may be partialy open.


QUESTION No. P228-2: I am working on a 27 inch SONY trinitron tv that when the power button is pushed you just get a click. I opened it up and traced out the dc output to the power converter board but am not getting an output from the board back to the main board.

Had the same problem. STRS6301 was bad.


QUESTION No. P34-9: Have a Mitsubishi CS2656R set. We are getting excessive retrace on screen. Cannot back adjustment down far enough to get a viewable screen.

Carefully check the crt board for bad solder joints and open traces at the 220v line at the crt board. I have had this problem on many Mitsubishi sets. Sometimes the coils on the crt board open. Also there are 2 switches on the crt board that are easily bumped. Make sure they are in the right position. It may also be possible to get the complete board from Mitsubish. As I recall they were not that expensive.


QUESTION No. P34-7: I have a Magnavox TV,model RH4816,25B1 chassis. The set will not lock in on the channel properly. It scans several times and locks in but will also lose AFT lock after playing a while. I have replaced the tuner, AFT coil, crystal and signal processor.

Try Replacing the Saw filter Y200. You may have also replace a resistor depending on which chassis you have.order the original part from magnavox,as it comes with instructions


QUESTION No. P32-5: I have a Zenith model SMS1943S in and need to adjust vertical height. Is this done via a pot or setup menu? If via pot which one? If via setup menu how do I enter the menu to do it? Please email replys to

Vertical size adjustment is r2106.


QUESTION No. P227-1: I have a SONY KV-27TW75 television that has intermittent distorted audio. It is not typical distortion as would accompany a poorly adjusted quad coil or bad output i.c. This is a very strange noisy, whistling distortion. If I inject audio into the external audio inputs, everything is fine. Switching from stereo to mono, or surround sound, etc. does not help. I suspect a problem in the stereo decoder or sound I.F. circuits. I have already replaced the I.F. Block #1-464-756-21.

You are correct! The problem is a defective "mpx/mts" decoder board located on te "A" board. The Sony part Number is 8-746-371-10.


QUESTION No. P217-4: RCA CTC167CS M# G26299TK 26" Floor mod. The vertical has collapsed leaving approx. 2" of picture across the centre of the screen. I have checked and replaced U4501. Also I have checked all caps, in this circuit as well as transistors.

Check CR4501 for open.


QUESTION No. P224-4: Have a Magnavox 13L4-04 chassis. Depressing On/Off switch and power relay pulls in, but set is dead.

Check R502, 47k 1/2w resistor.


QUESTION No. P127-8: Quasar TV model Number TT6267BW-1 chassis ALDC175. Horz. unstable, B+ in power supply to high.anyone seen this trouble?

When the regulated power supply goes too high the horizontal goes off freq to lower the high voltage. This is a modified xray protect cct in that the set does not shut down. Look at a bad regulator ic or possibly bad feedback resistor in the reg cct. Typically 10k.


QUESTION No. P130-2: Magnavox chassis # 25y100-00aa, Set will not come on until you unplug it and plug it back in. Intermittent--will go months with no problem, then start doing it again.

It sounds like the set is going into high voltage shut down. When this occurs the set can not be turned on until it is unplugged. I do not have an exact component replacement but check to see if the set has an xray adj, they commonly go intermittent on many sets. 2. Look for the xray protect line on the video processor ic. There will be electrolytic caps on this line to prevent the set from shutting down with rapid dark to light transitions in the video signal. They start to dry out and loose capacitance.


QUESTION No. P218-1: I have been running across rca ctc 175 chassis with low sound.

ANSWER 1: The low audio is caused by a bad eeprom. The cure is to replace the eeprom but be sure to read the contents of the eeprom before removing it or you will have to realign the tuner. Also remove the tuner cover and resolder the ground connections around the tuner and any the 4 lugs securing the shield to the board look carefully these tuners can have more bad solder and may cause your new eeprom to fail. If you want to confirm eeprom is causing audio problem remove collector of q1903 audio mute transistor, audio should return to normal levels if it is the eeprom. Note on out of warranty sets I remove Q1903 and leave it out. You will not notice any difference and it saves the customer some money.

ANSWER 2: Short pin 29 of micro to ground, cheap and dirty way to fix audio prob. this bypasses the audio mute when the set turns on.

QUESTION No. P214-2: I have a CTC130C Chassis that blows the Horizontal Transistor on Power Up. When the transistor does hold I will get a ticking on power up. After several tries the set comes on and plays for up to 30 minutes before blowing out the Horizontal output transistor.

On the ctc130 the horiz o/p will run hot if you have bad ground connections between the pcb and case. Also resolder the connectors the the plugs are connected to in the tuner control module. This normally corrects this problem.


QUESTION No. P127-4: I have a J.C. Penney television, Model 685-4027, uses a Goldstar chassis. After it is on about 10 minutes the channel and volume controls stop working, it takes itself to Channel 9, and stops responding to the remote. After it cools off all functions return.

Goldstar chassis had a problem with static locking up the nicroprocessor. The cure was to stick a piece of tape on top of the microprocessor and ground it to get rid of the static discharge from the CRT.


QUESTION No. P28-1: I have a RCA ctc 158B chassis. Has retrace lines and poor washed out picture.

On the ctc158 chassis you will get a washed out picture or high brightness and retrace when the video buffer transistor is leaky. It is located down by the video i/p connectors. It will test good out of circuit, but will break down under load.


QUESTION No. P212-3: Samsung model CT334KA chassis K20 has no high voltage (low voltage power supply O.K.). Makes ticking sound once per second, but horizontal oscillator does not start.

Samsung k20 chassis will tick if the horizontal is trying to start. You may have an open horizontal drive transformer or shorted horizontal drive transformer. I have seen both cause problems.Replace 10uF(22 uF) capacititor in B+, and check 100ohm resistor between the base and the collector of the power transistor.


QUESTION No. P23-10: RCA ctc 167c no video, h.v. ok, sound. ok.

Check for a bad luma buffer transister on main board. Will cause all three video output transistors on collector to read low, around 80v or so instead of 200v. Picture was brite w/retrace.


QUESTION No. P120-4: I am working on a Samsung txb1940, no chassis number. No power just a click. Have B+ voltage of 157.2 on horizontal output transister, no voltage at base of H.O.T. No voltage on one side of T401 that leads to base of H.O.T. Just replaced the str30130 but output is 139.2 volts input is 165.6 Is this set shutting down because collector voltage is to high at 157.2? Is the t401 a transformer of some kind, and is it what feeds the base voltage of the H.O.T.? What could be wrong with this set? No raster and no high voltage just a click on power up.

I am not familiar with the model number but the problem sounds familiar. If the set uses the TA7644 IC as the horizontal oscillator, check the voltage at pin 33. It should be about 8 volts and is supplied by a regulator transistor (possibly Q403). The problem may be with one of the voltage divider resistors that sets the voltage on the base (39K). The resistor connects the base of the transistor to the 150 volt line, and in the problem I encountered, changed value to 130K, lowering the voltage at pin 33 of the horizontal osc IC to about 2.8 volts.


QUESTION No. P211-2: Sony KV-2792R with the sleep indicator on. The TV will not operate and has no sound. The main IC was replaced and the remote does work but does not turn off the sleep indicator.

Check if power relay clicks when first plug in, if it does then problem is in horizontal output, flyback, low voltage supply circuit, missing low voltage supply causes sleep light to turn on. If power relay does not click check relay, relay driver, standby supply circuits. Look for open resistor around Flyback that feeds 26V line to vertical circuit. Possibly R-155 1 or 1.5 ohm.


QUESTION No P27-2: RCA CTC175C chassis does not power up. Sam's does not show a photofact for it but using one for a CTC177 I believe I may have a low voltage problem at the power switch feeding the micro U3101.

Check ypur eeprom i.c. if voltages less than 5volts change it.


QUESTION No. P18-3: Customer has dropped JVC tv. need new picture tube A68KRQ58X. Something loose inside tube. Will any other tube work?

Possibly available call 800-548-0575. be sure that the replacement tube is an A68. If you check on side of the tube towards the edge of each sude there will be the deflection and angle make sure that both tubes match.


QUESTION No. P19-1: CTC146 will not lock on channels. I have done all the tuner stuff and replaced the eprom. I disconnected cable and set up plugged then plugged back in vcr (3) will make it lock on. New tuner.

If you have the remote try punching in the stations like 12, 11, or 05. If this works fine but does not autoprogram all you have to do is adjust the aft coil but not much.


QUESTION No. P115-2: I have a RCA TV model # G35310WK, Chassis # 169JA2, that will not power up. It seems to be completly dead.

When your set is pluged in you should have 140 dc or about on your horziontal output. If you do not then check the primary of the switch mode power supply. If it is, a common problem on this model is the sound output will short and keep the set off. Pull the sound output out and try to turn it on.


QUESTION No. P127-6: Goldstar Model CMT-4445 13" TVappears to run normally, and then intermittently the picture starts to pulsate drawing in and out from the sides. It seems to be more prevalent with brightness turned up. Some times the set goes into shutdown when the picture starts the pulsating. The shutdown is first accompanied by a high pitch whine. The flyback core seems to be warmer.

It is likely that your b-plus for your horizontal output is changing. Monitor it. If it is go to the regulator and componets around it.


QUESTION No. P128-5: I am working on an RCA TV, model number F27227EM/ chassis number CTC169CF2, with a washed out screen and a green retrace line can be seen. If I adjust the Screen control fully counter-clockwise, the problem will go away and the picture will sharpen up, but will then appear again intermittently after the TV warms up.

Bad picture tubes are common on this chassis.


QUESTION No. P127-9: I have a 26" NEC TV model # CT-2660A with intermittent sound problem, does not seem to come from intermittent connections or thermal related.

I have had several of these with very small solder breaks on pins 32 and 33 of the "jungle" ic. I believe it is IC501. The breaks are so small it is hard to see them with the naked eye. Intermittant audio is caused by (believe it or not) a defective i.c. socket. Remove IC 201 and the socket for it. Replace ic201 directly in the board and solder it in. Throw socket away and do not put another socket in. I have done this repair many times, so I know it will fix set


QUESTION No. P17-2: I am having some problems with a RCA tv with the chassis CTC-175a. The system seem to be dead but it has 148 volts on the horiz. output.

RCA (GE) has has a techline that will help anyone in our field. You do not have tobe factory authorized but I suggest you have your Scope and DMM ready for use. Schematic not needed but helpful. If your not familiar with tech jargon do not call as they will get UPSET. 913-541-0402


QUESTION No. P123-2: I have a GE 25PM4860 with PM-C chassis. The problem is in the tuner control module, the volume will not change and the tuner is stuck on channel. The module is NLA. Anybody ever tried to fix this module?

Call Terrell and Nobis. They repair for around $35, 800-344-5545, 513-821-2298.


QUESTION No. P120-3: What causes a T.V. to send A.C. through coax? Normal repair from Cable Co. is place a Matching Transformer between T.V. and coax keeps A.C. from feeding back and impeding signal flow to T.V.

AC is passed through the cable because there should be a "Isolation" device in the coax inside the TV. Your set problem is an older Quazar and the "Isolation" device is made as part of coax cable going from the tuner to out side connection. The device is bad or someone replaced it with a standard cable.


QUESTION No. P114-3: I have run across several 25-inch Sharps with intermittant glitching that simulates arcing of some kind but it isn't. Then the set will go dead and you hear a slow tic-tic but as soon as I open the set it comes on and the problem does not recur until I have left.

I spent several hours chasing same problem. It turned out to be cold solder joints at main board connector to the yoke or flyback transformer.


QUESTION No. P17-3: I have A RCA Model Number F27671SE Chassis CTC 177BE. I have replaced the Eprom and soldered all the standard connections. The problem is that the Vertical will not lock in picture rolls.

I have found the problem to be IC "U1001", LA7610 or RCA part number 215524.


QUESTION No. P114-2: I have a sharp tv 20l series and a zenith 25" with the same problem, after two min. the picture gets a black square ih the middle of the set all you can see is about 1" of picture all the way around the screen.

This problem is because in your close caption settings is on and set wrong! Turn off or change setting of close caption and this will fix trouble. Note this is not in owner manual.


QUESTION No. P1211-11: RCA VR270 no power. Component tested, checked ok. Power tested will not go past the transformer.

It sounds as if the power transformer may be open. However you can remove the questionable leads from the circuit either by unsoldering or unpluging, or if need be cut the trace of the Pc-board to determine first if you have continuity between the transformers leads. If you cont. and it is not shorted then the possibility may be a short on the secondaries circuit. I am not shure if this model has a fuse or circuit breaker in the primary of the transformer or not.


QUESTION No. P1223-2: Is there a method of troubleshooting the type of switch mode power supply as used in the Hitachi 2508 CTV. this uses a TDA4601 IC as the switch control.

Hitachi and other makes TDA sw/mode PSU: Change 270k resistor. Change 3 electrolytics near IC. Change chopper transistor. Change IC while the IC and chopper are removed. Check values of resistors with meter. If the main chopper transistor has not failed it may only be the 270k resistor otherwise change all suspect parts in one go or risk chopper failure on power up.


QUESTION No. P1220-4: I have an rca tv with chasis # ctc175 model # f20301sf with a problem of picture distortion and loss. Also there was only 1/2 the normal audio. I resoldered all points to include the shield.

Eprom is bad - replace. Make sure you get all the setting from the old Eprom before replacing.


QUESTION No. P1125-3: I have a Sanyo colour TV Model: CEP 6022. With the following symptoms; sound is okay but no picture; does not seem to tune, snowy raster.

Although your particular model number is unfamiliar, I have taced "dead" tuner problems in a number of Sanyo televisions to an open supply resistor from the IHVT. Possibly R-508?


QUESTION No. P1212-1: I repaired a RCA CTC177AF, the original problem was the picture drops down leaving a blank spot at the middle, it will clear for a while when bumped. One day, when I turned it on for a while the picture drops and clear, but I could not turn it off, channel, volume up and down. So I had to unplug the power and plug in again, but the set went dead. Measuring the B+ and 12v from Swiching Power was ok, it was look like the Micro controller chip not working.

Remove the bottom of the tuner cover and resolder the ground connections and any other large connections that might be bad. If you still have problems you may have a bad IC.


QUESTION No. P1211-2: Have problem with an RCA TX825. Symptom is intermittent power-on. Most times unit will power on. The unit's clock will also lose time, approx. 10 min. per hour. Static check of components proved negative.

Changing TP15 and DP02 restored normal operation.


QUESTION No. P126-2: I have a magnavox t.v chassis 25c-04 with R403 blown, i think that this is a standard nap 120 ohm thermistor but I am not sure.

R403 is a degaussing thermister. I am not sure of the value but you can try 120 ohms and see if the set comes on. It will not hurt anything. Try ECG or NTE's line of Metal Oxide Varistors (MOV). choose one with 140v AC rating. I have used many times with success.


QUESTION No. P1113-3: Magnavox 13L4-04 chassis. Relay in power supply just keeps going on and off.

Change Regulator.


QUESTION No. P117-5: CTC 120D-1 Chassis Model FLR620TR, RCA. Keeps blowing H.O. T. Works for a short while but bends inward at middle of sides. Flickers and bends vary with brightness. B+ to pincussion PCB 125V, Damper diode ok (cold test), all caps on horizontal and pin circuits ok, must have checked all components but while set is off due to transistor blowing before enough time to check.

Replace the damper diode. A cold test cannot test for leakage.


QUESTION No. P125-1: I have an RCA model 25gt537 chassis ctc 177 af2 that cycles three times and then goes into shutdown when first turned on.i disabled the shutdown circuit and the set turns on but the horizontal frequency is off (too high).

Get into programming mode.. First adjustment is setting horiz. frequency . Adjust for slowly moving horiz lines. If you cannot adjust suspect the EPROM. If you replace the EPROM you will have to perform the complete set-up including re-alignment of the tuner. Consult service manual for details.


QUESTION No. P1114-5: Sony KV-27XBR51, no video or audio from tuner RF input, and no monitor output. Has RF noise with no raster. Works fine if input to video 1 , 2 or 3 then also get monitor out OK. Does not seem to be the tuner or the IF, testing with a tuner sub.

Bad VIF module, resolder AFT coil inside module, inspect other solder joints while you are there. Replace with new module if this does not fix it.


QUESTION No. P1121-3: I have a TV Sony KV-2781R, the picture was foldover and only about 5 inches in middle of screen and also reduced the horizontal size. I had checked the vertical frequency, it went up and alway changed about 200hz to some Khz.

Sounds like main regulator IC STK3035 is not working, check 135v at output of regulator out TP. Also check shunt resistor 200 ohm 20W, low supply voltage will cause vertical circuit not to work properly.


QUESTION No. P1125-4: I am working on an RCA television that had the typical intermittent snowy pix and vertical problem, so I resoldered the appropriate connections. However, the customer said that the audio was intermittent and now is missing. Could this mean that the eeprom is defective? The only voltage to the audio ic is the 24v line. The volume display does function properly but seems would seem to be muted.

It is indeed most likely the eeprom. It is intended to mute the audio momentarily so you do not hear a pop in the speakers. The eeprom is not unmuting the audio and should be replaced. Be sure to write down the chassis and tuner values before replacing though, so you can reset the new eeprom.

A second answer: Remove the mute transistor and just leave it out. I think it is Q1903, surface mount.

A third answer: Also the muting problem may be caused by the set being in mute make sure to scroll down all the menus and hit the reset I bet your audio returns alss there is a menu or option thats allows you to turn on the speakers turn them on and away you go.


QUESTION No. P1125-1: I have an RCA model CTC187 in for repair that has an hourglass effect. Looks like a pincushion problem. Has anyone had this same problem and gave you give me an idea of the correct place to start looking. Picture and sound are perfect other than being bowed in on both sides an equal amount.

The problem is that you have a bad filter cap in you power supply which is passing Ac.It usually is the largest capacitor in the set mounted toward the front

2nd answer: Possibly the pincusion problem is caused by a faulty cap and diode, they are a blue rectangular cap and the diode is in front of it. Sorry I do not have the values or locations for you but they are very close to the heat sink near the center of the board. The blue cap will bulge a bit if you look closely.


QUESTION No. P1114-1: GE Model 25GT506 Started out with vertical shrinking then no video at all. Audio yes.

Resolder grounds under tuner shield and around micro shield also see answer to question number P1022-2.


QUESTION No. P117-6: I have heard that RCA produces a database that has chassis or model or sympton listings. Where is this available?

It is called "FIXFINDER". Updates are $39.95 per year. avail from any RCA distributor.


QUESTION No. P1022-2: I am working on a 27" RCA TV model F27672ET chassis number CTC187BD2 that has no power. (The GE model 27GT615 chassis CTC177BH2 uses the same main board)

Many problems on this chassis can be traced to poor ground connections under the tuner shield. Remove the tuner shield and take a good look at all shield grounds. Also if you find the horz output transistor to be shorted check for and open cap (C4407) .047uf PN#214754. The ground around the tuner can also cause eprom and microprocssor failure.


QUESTION No. P108-2: RCA CTC-136 chassis ticks very rapidly when you apply power. If the startup scr is bypassed it has a normal raster, but appears to be missing tuning voltage, tuner lites and some other voltages. The tuner just drifts around, but there is normal "snow" similar to having no antenna connected. Whatever voltage that holds up the starter circuit is missing.

Check C422. It may be leaky.


QUESTION No. P930-4: I have a Toshiba CTV Model No.CF13C20 with no audio outputs and all caps OK. Has anyone seen this problem or have a copy of the audio circuit?

I have a schematic diagram for CTV Toshiba CF27E50. It seems it has very similar audio circuit as CF13E20.


QUESTION No. P1011-5: I am working on a Magnavox model#RP2590A102 chassis# 25T103-00BB. The problem is the only thing it will display is a single horizontal line across the center of the screen. I have replaced the IC that controls the vertical deflection but that made no difference.

Check for supply voltage (Vcc) at the chip. Generally this is a scan- derived voltage approx 24-Volt DC.


QUESTION No. P107-5: I have a problem with a Model: 27J233 Chassis: 27H1-50 TV. I already found a bad condenser C500. This is a SMT item but I do not have it's value. I have tried to obtain some schematic of this set here in Mexico to no avail.

C500 is a 330pF cap located in the Base circuit of Q500, horz driver transistor.


QUESTION No. P95-1: I am looking for information to obtain parts and service literature for Admiral televisions.

Check with Montgomery Wards. They now own the Admiral name.


QUESTION No. P923-1: Rca chassis # TX 825, dead. All the major componets check good, h.o.t., driver, fuses, etc.

Replace transistor TP15, RCA part number 198752. Note: the transistor runs quite warm and I have had non-RCA replacements fail. Check or replace zener diode DP02 and TR03 and zener diode DP05.


QUESTION No. P95-3 & P1219-2: I need the ECG equivalent for a Zenith horizontal output transistor numbered 1141-01 on the part. It is designated QX-3208 on the main chassis. Chassis no. 9-1101-1.

The complete Zenith part number is 121-1141-01 and should be readily availible through any Zenith distributer or Zenith repair center. BTW, the 9-1101-1 module is also availible as a replacement part. ECG equivalent is 2302 just add 121- in front for the Zenith part #


QUESTION No. P828-1: I have RCA Dimensia Model RVM2630F01 Jun89 CTC140S TV, cannot get the picture to sync, both hor. and vert., but the on-screen display stuff is synced. I have checked for bad solder joints. It sometimes syncs if just powered on.

ANSWER 1: Remove all traces of brownish, glue-like substance near U2300. . Also, check C2328, .01uf SM cap under the chip.


QUESTION No. P86-1: I have a TV Sony KV-2781R and I need the original number for the horizontal output transistor.

2sd1497 Sony pt.# 8-729-300-90


QUESTION No. P724-2: I am working on a GE tv model#8-2668. The tuner sometimes flips thru the channels by itself and the volume increases to max. When turned off, the tv will try to turn on by itself on at 1 hz. pulses. The tuner has been replaced with no change.

Check for spill on keyboard problem is caused by more than on input on command line at one time, picture tube face was probably cleaned and liquid spill on to key board.


QUESTION No. P722-8: RCA CTC-186A chassis. Set will play ok for any random length of time then it loses all brightness until power is turned off, at which time the set functions ok again. It doesn't appear to be thermal or mechanical in nature.

The first thing you need to do is repair the bad solder connections for the tuner shield and microprocessor. There are 12 connections under the tuner cover and all of the outside connections, plus hit e-16, e-17 jumper wires both ends. If that does not fix your problem check your eeprom data to see if it is way out of line. If not write it down and replace your eeprom. Then reprogram it using your old data.


QUESTION No. P711-1: I am currently working on a Sylvania VC8960AT01. When you plug it in, it emits a high frequency noise that slowly descends in frequency until it bottoms out with "white noise". The noise sounds like it is emanating from the power supply. I have no indicators, such as led display, power on indicator, etc.

It soulds like you have one or more electrolytic caps that are bad in the p/s. Also check all of your diodes on the secondary side of the p/s.


QUESTION No. P722-7: I am working on a rca tv with ctc156 chassis. It has vertical retrace lines and on startup it has no vertical deflection. The vertical deflection returns after about 10 seconds. Brightness appears to be ok.

Try changing the two ziener diodes that regulate the standby p/s.


QUESTION No. P722-3: I have a Panasonic ctj1000 that has hardly any vertical deflection. The vertical deflection is done in this unit with a AN5515 vert defl sip module. I think the module is most likely bad. Any help would be appreciated. The picture looks somewhat like the service switch is activated but it isn't and I do get the thin line when I activate it. There is about 1/5 of the picture on the screen and it is mostly in the middle of the screen.

There is a diode that is used to supply power to the vertical deflection IC. This diode may test ok with a meter and seem to function and behave properly. However, it fails in a way that will not allow enough current to flow thru it that the vert defl output needs.


QUESTION No. P75-2: I have an RCA CTC176E chassis with no pix and no sound. High voltage comes up with light red raster as soon as the set is plugged in (blank screen with no sound), and none of the front panel controls work. I suspected the system control microprocessor but replacing it made no difference. All the standby and run voltages are present.

First check your CRT with a crt tester. Resolder the tuner and mircoprosscer sheilding. Replace your EEprom and put your TV in the service mode. And program your EEprom. You might have a damaged EEprom. You must have a RCA service manual for your set to put in service mode. And program the EEprom with correct vaules. If you have more problems or are not sure how to proceed . You can RCA tech support at 913-541-0402.


QUESTION No. P520-1: I have an RCA Chassis CTC130B that works fine until it warms up. After several hours the sound will go to full volume, the picture is snowy and none of the controls have any affect. You cannot change channel, adjust the volume or even turn the set off with the Front Panel On/Off button. The only way to recover is to unplug the AC input for a moment and turn the set back on. I have tried to isolate with Cold Spray without much luck. This is the same set that I fixed by replacing the HOT as someone here suggested. Initially it had the old Tick, Tick, Tick symptom.

Check the low voltage regulator output when first powered up and seeming ot work ok and compare to its outputs when things start acting strange, i.e. no response from controls. See if that takes you anywhere. If low voltages are off controlling circuits may not function properly. Check for bad connections or thermal senitive caps in mtt tuner/ controler module Resolder MSC module where plug connectors are.


QUESTION No. P51-2: Would like recommendations on books, videos or correspondence courses to learn more about repairing televisions.

My favorite book on the subject is: Troubleshooting and Repairing Solid-State TVs by Homer L. Davidson. See ../books/books.htm for this and many other good technical books.


QUESTION No. P52-1: RCA CTC169 intermittant power on, 15v line is measuring about 10v-11v. Unit cycles on and off three times then shuts down. Unit will power up at times and remain on for different periods on time, but will eventually shut down.Unit regulates at 142.5v when power stays up, 15v line remains between 10v - 11v. Floating Jumper JW324 allows 15v line to return to normal. Q4105,Q4106,Q4107 and Regulator IC have been replaced with no change in symptom.

Check C4118. It is a 47 uF capacitor off pin 16 of U4101. Check CR4118 the 15v diode. It checks good(almost) but breaks down under load. Other syptoms include shutdown and no color. Highly Intermittent. Part#164590 RCA.


QUESTION No. P429-3: I have a RCA Model F2031SF Chassis CTC175A Color television with no picture.

I've had two units with no picture and no audio. Both had a cracked chassis on the flyback side and no obvious signs of being dropped. Repairing damage to the circuit board corrected both sets.


QUESTION No. P42-5: SONY TV KV-25XBRII Television demonstrates intermittent behaviour. Screen shows reduced luminance then can be returned to normal by physically jarring television. Suspect cold solder joint or defective oscillator crystal somewhere in video signal path. Audio is normal.

Check the video delay line DL301 on the A board. A very common problem in this model is a cracked solder joint on the legs of the delay line.


QUESTION P32896-1: An RCA CTC 146 L does not tune the lower VHF band (channels 2 through 6). It looks as if the band switching voltages are OK. I drove VT with a variable supply and was able to tune through all the channels in the upper three bands (7-22, 23-55, and 56 -99) but varying VT in the low band didn't do a thing (just hash on the screen). My guess is that the VCO in the tuner is not functioning when the lower band is selected; is there a way to verify this? Does anyone ever try to repair tuners?

The problem you have is a bad solder connection inside of the tuner and is a very common problem with this chassis. One of the coils inside of the tuner is cold soldered. Off the top of my head I think it is L102 but to be safe, just resolder all of the coils in the tuner. Just be aware that the coil in question (L102 I think) is SOMETIMES covered with wax so examine carefully. One final note, the solder connections look ok but resolder them anyway.


QUESTION No. 21996-7: The problem child is a 27" console mitsubishi TV about 10 years old. It has developed an intermittant crackling noise with associated breaking up and fliPing of the TV picture. I thought this was a simple arcing problem in the high voltage/horizontal oscillator section of the set. However, everytime that I remove the back f the set and run it that way the problem disapeers!!! I have cleaned the high voltage section and looked for arcing but see nothing wrong there. The inside surface of the back cover of the set is also undamaged so no arcing there. When I replace the back of the set it starts working with no problrms for a few days. There is also something thermal going on since the set stops "crackling" after warming up for a few hours. Should I just replace the flyback transformer, or has someone actually seen this situation? If anyone has any clues please help me out.

I have seen arcs in the CRT socket cause this problem. Best bet is call and see if Mitsubishi has a High altitude socket for this set and replace it with that. If not, you still need to replace it.


QUESTION No. 2196-3: I have a Sony KV-1397R 13" color TV with intermittently drifting tuning. When problem shows, all channels are still available, and with plenty of RF gain, but drift toward the no-color direction (not toward the grainy color direction) until finally the AFT voltage from SIF-VIF module begins cycling. Tuning follows. Gets stuck in this cycling mode which lasts several seconds per AFT cycle. Only one AFT signal is active at this time, I believe the 'down' side. No action at all, even when changing stations, from the oPosite AFT signal. Schematic gives no help to one as unfamiliar as I with the theory behind this tuner's control loop.

ANSWER 1: In answer to my own question, tuning loop aPears to work like this: Control IC tells tuner desired channel, tuner responds, control IC watches AFT UP and AFT DOWN signals from VIF-SIF module to decide whether correction is necessary. In this case, VIF-SIF module is sending erroneous AFT down signal until control IC makes a decision that it's too far off ideal channel frequency, so tuning to center channel, at which time incorrect AFT down signal again tells the control IC to detune tuner. Shorting the input to the AFT DN IC, which is isolated from the VIF-SIF by a P22K resistor stoPed the hunting, but in the meantime of course killed any AFT action. Replacing VIF-SIF ($44!) cures the problem.

ANSWER 2: The problem you are experiencing is caused by bad connections in the SIF-VIF module. To repair the problem, remove the IF module from the main board and remove the shield case from the IF module and solder the internal pins and any other bad connections you can see on the pc board. Then reinstall the shield and solder onto the main board

ANSWER 3: Two common problems on Sony can cause this problem. Both are bad connections. The most likely, from your description is a bad solder joint in the tuner. You must pull the tuner, remove the sheilds, and check the joints where the sheild and cage are soldered. These crack. Carefully, resolder all grounds. The other is in the if can. Open the can and resolder all connections on the agc control, and grounds on the board.

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