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Panasonic ct-31g30 TV: Audio, OSD and power switch problems

I'm wondering if anyone out there can give me some advice about a recently acquired TV. It's a Panasonic ct-31g30 (32").

When I first powered it up, all was well; all functions worked properly. After about an hour, the following things occurred:

  1. The volume would, at several-minute intervals, briefly blast at full volume, then resume its previous setting

  1. The OSD text became distorted and difficult to read

  2. The power button stopped responding.

Once the set cools down, all functionality returns to normal.

I'm guessing that the issue is an ailing EEPROM, but I'd like confirmation of this (or another guess as to what the problem might be), and if known, the part number of the suspected chip.

Thanks very much!! Sean

Reply to
mcseanmcf
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Pull out the chassis and turn it over ,get out your magnifying glass ( A Large One )and look for bad solder connections and resolder them. Reassemble and try...

Reply to
kip

Thanks for the reply Kip.

I had a look at the chassis last night, went over the entire board with a magnifying glass, and resoldered all pins on the ICs, header pins, and numerous other areas that looked suspicious. This morning, I ran the TV for about 45 minutes, and the same behavior occurred again. It seems as though it consistently takes 45-60 minutes for the problems to begin to occur, after which they are constant. One more thing- the TV was left on for a little over an hour yesterday, and eventually shut down on its own. The power button did nothing at that point, however I was able to get the set to turn on after unplugging and plugging it back in. Any recommendations on what else I could look at?

Thanks aga> Pull out the chassis and turn it over ,get out your magnifying

Reply to
mcseanmcf

Did you resolder the Horizontal sections ..like Drive Transformer, Flyback , Drive Transistor etc etc etc ..Not to mention the Relay regardless what those connections look like.

Reply to
kip

Yep; all of the above. Having Googled around a bit, it looks like the voltage regulators on these sets are problematic. Would a faulty VR cause such erratic behavior?

Reply to
mcseanmcf

Yep ..Is it a STK730XXX..???? or one of its associated components. < kip

Reply to
kip

Sorry for my ignorance, as I'm not that familiar with this model, nor do I have the schematics. I went on Panasonic's parts site and found the following IC's, each coming up as being a voltage regulator:

AN78M05 AN78L12 AN7809

I didn't see anythign with the prefix that you mentioned. Given how cheap the parts are, I may just order all three and replace 'em...

Reply to
mcseanmcf

I dont think those are your problem ... Solder all as I suggested first kip

Reply to
kip

Welp, I soldered everything as you suggested, and replaced the two voltage regulator ICs, but no success. As I was working on the chassis last night, I wondered aloud if the problem concerns a component that is attached to a large heat sink-- the set is fine for 45 minutes to an hour, then the problems begin.

Any suggestions about what to try next? I've resoldered just about every point on the chassis (in addition to the spots that you suggested).

Thanks again, Sean

Reply to
mcseanmcf

What is the part number on this large heat sink ?/

Reply to
kip

You were correct- the regulator is a STK730-020. I just replaced that, and also found a service bulletin that recommended replacing the HOT (Q551) and two ceramic caps (both are 2.4K/3W).

So, I replaced everything, and as bad luck would have it, I'm no longer getting high voltage when I turn on the set- the replay clicks on, however the tube does not fire up. I'm going to retrace my steps to night and see what possible could have gone wrong. Arrrgh.

Sean

Reply to
mcseanmcf

Sorry- ceramic resistors. Not quite awake yet... And the upgrade kit for the HOT was TXANV0598SER. All parts are genuine replaecments.

Reply to
mcseanmcf

Sorry- ceramic resistors. Not quite awake yet... And the upgrade kit for the HOT was TXANV0598SER. All parts are genuine replaecments.

Reply to
mcseanmcf

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