1979 Sears Solid State TV popping

[kb12]

Hi, I am new to this forum and to vintage tvs. I just bought at 1979 solid state sears TV for $15. The picture looks great but a couple weeks ago every time I turn it on it makes a loud popping noise. Sometimes the noise is faint, sometimes it is really loud. Nothing changes in the picture though, still looks good. What could this be? Is there anything I can do? Thanks for any help you can give.

[DaveWM]

what is your level of exp on working with electronics?

[radiotvnut]

The noise is most likely from a high voltage arc. You could have a dirty 2nd anode connector on the CRT, a crack in the anode connector or high voltage cable going to the CRT, a cracked high voltage tripler (if one is used), a cracked focus divider (again, if one is used), a cracked housing on the flyback (HV) transformer, a CRT socket that is arcing for whatever reason, or a poor aquadag ground connection on the CRT.

Just be aware that there is around 25,000 volts on the CRT second anode and around 7 to 9 KV on the focus lead going to the CRT socket. And, there will also be up to several hundred volts in parts of the video output stage. Also be aware that the CRT (picture tube) and other capacitors in the chassis can hold a nasty charge, even with the TV turned off and unplugged.

A model number and/or a picture of the TV might be useful, as there were many different suppliers of TV's to Sears.

[bgadow]

If the picture doesn't change at all when this happens, it could be, maybe, a bad cap? A HV arc would have to make some sort of disruption in the picture, I would think.

I did have a late 70s Sears TV given to me and it worked fine except one of the caps was bad. The symptom was some sizzling and a mild burnt smell. I have had sets where a bad black beauty would let out a distinct "pop!" at regular intervals, as gases would be vented. I don't know that this set would use any of the old style caps, though. The closest maybe would be a ceramic-tubular (the infamous white El-men-co) but 79 seems late for that, at least from Sears.

[jeyurkon]

Originally Posted by bgadow

If the picture doesn't change at all when this happens, it could be, maybe, a bad cap? A HV arc would have to make some sort of disruption in the picture, I would think.

I did have a late 70s Sears TV given to me and it worked fine except one of the caps was bad. The symptom was some sizzling and a mild burnt smell. I have had sets where a bad black beauty would let out a distinct "pop!" at regular intervals, as gases would be vented. I don't know that this set would use any of the old style caps, though. The closest maybe would be a ceramic-tubular (the infamous white El-men-co) but 79 seems late for that, at least from Sears.

I'm not sure why, but to me HV breaking down sounds more like a "snap" and a condenser breaking down more like a "pop". I'm inclined to vote "cap."

John

[DaveWM]

I wonder if we lost our OP'r....

[jeyurkon]

Originally Posted by DaveWM

I wonder if we lost our OP'r....

I hope not. I've worried about other posters, but they'd eventually get back to the thread.

John

[kb12]

Thanks for all the replies! I do not know too much about repairing electronics but I just wanted to make sure this is not a safety hazard or something that can be easily fixed. Now that I think about it, the sound is more like a snapping noise. It doesn't happen every time I turn it on. I was gone for a few days this weekend and came back and was greeted with a very loud snap when I turned my TV on. I have included a picture if that helps. Thanks

[radiotvnut]

That looks like a Toshiba built TV. One thing you might do is operate the set without the back in a dark room. If anything arcs, you should be able to see it. Of course, it will never act up as long as you're looking for the trouble.