Sylvania model ca8112wh
chassis ident number- e210002-1464351
mfgd- april '78 (<-figures....just hit 30)


a while back i posted about a sylvania TV i have, at the time it had some issues making noises and came to find out that the supposed 'repairman' actually did fix something (tripler). Ive been using it since then without incident till tonite. I was about to go to bed, i was watching Mythbusters when at the very end of the episode (closing credits) and video went out. at first i figured it was on the cable company's end but kinda thought it was awful clear blank raster (no static or anything) to be that. I got up and switched channel and it was still blank. I have sound, i have raster, just blank like the tuner is not workng. No magic smoke or any noises, just stopped displaying video.
Now be gentle, im a mechanic. i concider myself a decent mechanic but im still a just a mechanic, and while i enjoy electronics and the like ive never done much other then fixing a few old radios (recaps), and the regular stuff at work dealing with electrical issues (i work at a dealer so we see all the "bring it to a dealer" issues).
can you help? does anything commonly go bad on these to kill video? No matter what im not getting rid of it, just wanna save some money and get satisfaction out of trying to fix this myself. Any ideas would be appreciated.

Hi, I don;t know about that specific model, but I'd resolder the entire crt neckboard (video-output board) just to rule that out, and then look for bad caps and connections on your power supply board.

Hi, I don;t know about that specific model, but I'd resolder the entire crt neckboard (video-output board) just to rule that out, and then look for bad caps and connections on your power supply board.

yeah i guess ill open it up tomorrow or over the weekend, just hopin someone may have seen a bunch of these have issues and be able to shoot off some parts to check. Im still accepting ideas.

thanks again everyone. Anyone have a schematic for this?

k, most likely be calling this place "dragon tv repair" monday but i figured maybe itd roust some more brainstorming if i give a few more details:
i played around with stuff today to try to give you an idea of what does and doesnt work.

Tint controll seems to make the black go from greenish black to purpleish black-so that seems ok. Horizontal hold makes the screen flicker (i assume if there was a picture it would be rolling). brightness and contrast react normally....on the blank raster. The tuner audio works fine, no video on VHF or UHF. I dunno...maybe this helps. i opened it up and didnt see anything obvious (bulging caps or bad solder joints). the crt neckboard doesnt have much on it, a few resisters and thats about it. looks like individual color drive is on the main board...side by side red, green, and blue (judging by similar layout of components), but i assume thats all working as i can change the tint of the 'black'.

Maybe the digital switchover has already happened at your house :)

Lol. Keefla I recommended resoldering the neckboard because on most sets this is where your video out transistors are located. If they aren't, then I would go ahead and find those since they're high heat devices....Also check that the brightness/contrast pots aren't losing contact with the board.

That should be an E21 chassis. Check the service switch. Switch it back and forth a few times. All video passes through this switch, and dirty contacts can cause you to loose the video. Back from the switch is the video amp transistor Q904 (I think), it will cause no video as would the failure of the video buffer transistor Q902 (I think). If you have sound then everything up to the sound take off should be ok. This leaves the switch, about 3 transistors, and the low level IC for processing the video. As always 30 year old caps and out of tolerance resistors can kill a transistor, or IC, and bad solder joints in this area could be a problem. There isn't much on the neck board as you noticed other than some biasing resistors.

Bill R

That should be an E21 chassis. Check the service switch. Switch it back and forth a few times. All video passes through this switch, and dirty contacts can cause you to loose the video. Back from the switch is the video amp transistor Q904 (I think), it will cause no video as would the failure of the video buffer transistor Q902 (I think). If you have sound then everything up to the sound take off should be ok. This leaves the switch, about 3 transistors, and the low level IC for processing the video. As always 30 year old caps and out of tolerance resistors can kill a transistor, or IC, and bad solder joints in this area could be a problem. There isn't much on the neck board as you noticed other than some biasing resistors.

Bill R

Bill, thanks for the suggeations. it is an e21 chasses, and according to the transistor layout sheet inside the set it lists Q904 as the video driver and Q902 as the video amp (so you were on target just backwards....i say thats close enough for probably not having seen one for 20 years!). So i will remove and test them. I did try the service switch and it seems fine, i saw no hint of video when switching it back and forth, even hit it with some contact spray just to be sure. ill post back as soon as i test the transistors and let you know.

Bill,

i checked Q902, Q904 and q202 (video buffer). all seem fine, 800 or so ohms b-c and b-e, even collector to emmitter didnt show any continuity on my meter on the 2 meg scale. so i figure theyre all ok. any ideas what voltages i should be getting on the pins on the low level video ic? no bad solder joints were seen and no obviously bad caps.

Here's what I have on the Sylvania E21 chassis. Sorry for the mess - it's an old DBIII+ database, converted to text, then to Word, then to PDF for posting.

Disclaimer - I've not worked one of these sets in more than 5 years and haven't even looked at the Sams for it.

Hope the tips are useful.

Cheers

Here's what I have on the Sylvania E21 chassis. Sorry for the mess - it's an old DBIII+ database, converted to text, then to Word, then to PDF for posting.

Disclaimer - I've not worked one of these sets in more than 5 years and haven't even looked at the Sams for it.

Hope the tips are useful.

Cheers

thank you for that file, no need to appologise for the layout, it was perfectly readable. i found a couple that kinda match the symptoms...namely dark picture...but i have no picture at all....maybe ill start by checking those components (caps it loosk like)...see where i get with that. as always still open to suggestions and thanks you all for your help!

Good luck in getting her going again. I'm no Sylvania buff but they were always very interesting sets to me. :thmbsp:

Sorry about the number mix up. I pulled the schematic and looked again. Q904 is the video driver, Q902 is the video amp, and the video buffer is Q202. The video comes from IC202 which is called the low level detector. It contains the video dector and first video amp. From there signal passes through Q202, Q902, then Q904. If you have a scope you can look for video on pin 4 of IC202, if it is there check the emitter of Q202. If you have no video there then look at the base of Q202. If video is ok at emitter of Q202, move on to Q902 base. There is a 5mfd 25 volt capacitor (c247) for coupling Q202 to the base of Q902. From the collector of Q902 video passes through the delay line and to the base of Q904. It then goes from the emitter of Q904 through the service switch then to the red,green, and blue output transistors and on to the crt. I do not have any voltages listed, the scope though would be the easiest check since you could just follow the signal path and look for the video signal. Prime suspects are the service switch, Q904,Q902,Q202,IC202,c247, and I have seen open delay lines. The 24 volt power supply is used here, but also in the audio section, so since you have sound still the 24 volt supply is probably ok.

Bill R

bill,

that info will be extremely helpful, i do have a scope thow its on lend to a friend right now. Ill go grab it back for a few days thow. ill be able to do that tomorrow after work and should have a better idea of what part of the chain is broken for you by friday. thanks again for everything ill keep you posted.

update time,
grabbed the scope today and checked at pin 4 of IC202, had nothing. I tried injecting video at pin 4 (to check the rest of the chain and found a scrabmled picture...however i found that if i inject video into pin 2 i get a deciferable picture on the screen (vcr setup screen). so i guess its before that IC? is pin to the input or am i just bypassing something ? what would you suggest i check next? I tried to find a pinout but to no avail.

Input is on pin 7. Pin 2 is however part of the video detector circuit. Sounds like you may need to replace that IC. If you inject video at pin 4 and get video, but no video when using pin 7 the IC is bad. You could just look with the scope though. The output from a vcr may be to high for a proper picture.

Bill R.

Input is on pin 7. Pin 2 is however part of the video detector circuit. Sounds like you may need to replace that IC. If you inject video at pin 4 and get video, but no video when using pin 7 the IC is bad. You could just look with the scope though. The output from a vcr may be to high for a proper picture.

Bill R.

bill,
first i want to sincerely thank you for your time, i hope you know how much help your providing. Secondly tomorrow i will try pin 7 (ill scope it). as it sits now i have nothing out of that IC on pin 4. will i have a video signal at pin 2? or am i just looking for any signal? Ill be the first to admit using the vcr was crude but i figured what the heck, and it gave me hope that I can actually fix this (thats what really amazes me). Coming from a mechanic's point of view you guys are geniuses!

You will see some form of video on pin 2, as well as pin 3. Pin 7 is the input, 1 is the output to the sound circuits, and pin 4 is the output to the video circuits. Keep in mind that the signal on pin 7 is before the audio take off and before the video detector stage, so the waveform will be an IF waveform, but it will be there. Since you said you have audio, you should have signal at pin 7. Pin 2 and 3 are the 45.75 mhz tuned circuit for the video detector stage of the IC. Be sure to touch carefully touch up the solder connections to the IC, as they can cause problems. Using a vcr is not that crude, but the output from the vcr is composite video so injecting at pin 7 probably will not work. You could use it to check after the IC as you have done. There would be an impedence mismatch, but with a pad to attenuate the signal and a coupling capacitor to isolate it from the DC in the set it could work. I wouldn't expect a perfect picture, but any picture would indicate that the video path was working from that point. The Sylvania part number for the IC is 13-39060-1. It will probably cross to an NTE/ECG replacement.

Bill R

k, i checked at pin 7 and had something (my scope is only a 30mhz so it was out of range) but by playing something through the tv i was able to change the signal on pin 7 (amplitude wise was higher verses static on TV). i checked for sound out at pin 1...didnt really see anything (thow im sure its there as the sound works). pin 2 and 3 the same, nothing, but if it was 47mhz at may have been to low of a signal and too out of range for my scope. and for one more check i injected video in pin 4 and got a very out of sync but mostly correct (color wise) picture. injecting it at pin 2 or 3 yeilded a more correct picture that was badly smeared and washed out (but readable and in sync). so thats where im at. does it seem like that IC is dead? If so where may I find another one?

Sounds like a bad IC.

Bill R

part is ordered, 3 days to process plus a few to ship and we will see how it works out. it was $2.80.

By the way any scope over 10mhz is fine for tv work. The bandwidth is only about 6mhz. The tuned circuit is at 45.75mhz, but only a few megahertz wide. So your scope is fine. Hope the IC solves the problem. At the shop that repair would cost about $70.00 around here, maybe $100.00 if they have to pick it up. It is a shame how many of those sets were scrapped because of a problem like that, in favor of a new set.

Bill R

Agreed. Hope it works out for you. I'd love to see a picture of the set as well... I never find Sylvanias 'round here

By the way any scope over 10mhz is fine for tv work. The bandwidth is only about 6mhz. The tuned circuit is at 45.75mhz, but only a few megahertz wide. So your scope is fine. Hope the IC solves the problem. At the shop that repair would cost about $70.00 around here, maybe $100.00 if they have to pick it up. It is a shame how many of those sets were scrapped because of a problem like that, in favor of a new set.

Bill R

I will definatly keep you posted on the outcome. if it for some reason isnt the issue i hope you will bear with me for some more testing, thow it looks like the only possability, for under 3 dollars if its not then thats fine. hope it fixes it thow cause its been a week now and ive been using a b/w zenith hybrid set from '75 and i dont want to put too many hours on it, plus the picture on the sylvania is awesome. i was so happy when i saw it show a picture after injecting video into the output of that IC (granted it wasnt anything useable but proved to me there was hope. Anyway looks like another week maybe and we will have our answer. It wasnt easy finding a place to get that IC from, it ended up being from Prelco Electronics in NJ, they had a "nap" equivilant (says NAP in the manufacturer list) which comes up as "low level video detector" and crosses back to the Sylvania part number you gave (and matches the part number on the IC itself). Ill keep my fingers crossed.

update, my parts are on their way finally. got an e-mail this afternoon saying the check cleared (had to pay with personal check cause i didnt have a business account with them.) so my parts will be here most likely saturday or monday. in the mean time i figured id show you my temporary daily watcher (which also has an amazing picture, this is an amazing set), a Zenith f1336c3 tube hybrid. As usual the pictures cannot do it justice.

First I want to thank everyone who helped me on this set....Bill R you were very patient and very helpfull, all of you were a great source of knowledge....i think you can see where im going with this....as Bill correctly led me to diagnose...the low level video detector IC was bad. Replacing the IC brought back a full color picture....heres the details:

today in the mail came a box from prelco electronics, i gleefully opened it like a kid on christmass and found 1 IC-my low level video detector. i was happy to see it looked the same (you never know these days with internet electronics supply places). i removed the offending IC from the TV and popped in the new one. threw the cord on and figured id see what i get before i put the cord back into the back of the set and clip it in place and put the shields back on and whatnot inscase it didnt work. i turned on the power and waited....and waited....and finally....dimly....i got SNOW!! I immediatly shut the TV off and put it togeather fully, and buttoned it up, hooked it to the VCR and tried to get a picture for the first time in over 2 weeks. I had dim picture. twiddling the contrast and brightness controlls helped but the picture kept cutting out....i found the brightness controll was causing this so off with the back again (im getting good at this) and found that when i slid the back on i must have hit the brightness knob and cracked one of the solder joints....no worries ill solder it....well not tonite since my only soldering gun is at work (booo). So i couldnt get a picture of it in action BUT it IS in action...or will be fully tomorrow afternoon....when i held the brightness knob i got a perfect (same as always on this set) picture!!!! I really cant believe i fixed it....im so happy!!!! it cost me 8 bux after shipping.

Below is a picture of the blown video detector IC. tomorrow ill post pix of the set doing its thing again once i reflow the solder on that brightness pot.

Another one saved from the parts bin. Good work! Glad to help.

Bill R

Nice to see it's alive again!

Resoldered the brightness pot, as promised here are the pix. usual disclamers apply (camraphone, looks flwaless in person). one pic look like the blue convergance is off but its not .


Thanks a million again to everyone. This wouldnt be possable without the help you offered.

Glad you saved it! Now it should last until its CRT won't emit any more electrons (roughly 30-40 years lol) :thmbsp:

...

It looks good. You could probably reduce the vertical size a little so it doesn't cut off the text at the bottom.

yeah i touched that up a bit yesterday.:thmbsp: