Panasonic CT-36G22V gremlin I can't track down! - Videokarma.org TV - Video

MRX37 · #1 11-28-2008, 03:32 PM

Awhile back I sold a 36 inch Panasonic CT-36G22V to a close friend. When the TV left my house, it worked fine. when it got to his apartment, it developed some weird gremlin where even the slightest vibration, even gently tapping the TV will disturb the picture. The TV may also shut off by itself and needs to be whacked a few times before you can turn it back on. Also, sometimes the picture will collapse to a line across the middle of the screen. (no vertical)

Thinking there's a few bad solder connections inside the TV, I have so far resoldered the flyback, HOT, a couple other large transistors, and pretty much every connection in the power supply. I also scanned the board and touched up any solder connection that looked even slightly suspicious.

The board is free of any cracks or damage. This TV has a few cards plugged into the main board. I took out the card in the power supply section and touched up all the solder joints on it.

So far, the picture hasn't collapsed to a line yet, but it's been looking like it wants to, and even the slightest vibration will disturb the image. Also, I'm not certain but the image looks maybe a little too high, like the vertical height is a tad too high. I'm at a loss on where to narrow my focus to.

Findm-Keepm · #2 11-28-2008, 05:13 PM

Check the solder connections at the Horizontal Driver transformer - you can trace the connection from the base of the Horizontal output transistor. Aside from that, check the solder connections at IC801. That's all I have in my notes for the Panasonic "G" sets.

Cheers,

MRX37 · #3 11-28-2008, 05:26 PM

Quote:

Originally Posted by Findm-Keepm

Check the solder connections at the Horizontal Driver transformer - you can trace the connection from the base of the Horizontal output transistor. Aside from that, check the solder connections at IC801. That's all I have in my notes for the Panasonic "G" sets.

Cheers,

Pretty, actually very sure I resoldered that transformer. I resoldered a few transformers in that area.

Didn't touch any IC's... I guess that's my next step.

EDIT, IC801 is on one of those cards that plugs into the board. It's near the tuner can. I resoldered that ic, the card connector, and various other components on the card. No change. The picture still gets disturbed by as little as tapping on the side of the TV.

All transformers anywhere near the HOT have been resoldered.

MRX37 · #4 11-28-2008, 06:29 PM

I can't isolate it. I tried tapping areas of the board to try and pin it down. No matter where I tap, or how slight I tap, the picture gets disturbed. Even slightly tapping the CRT neck board will disturb the picture, and the CRT neck board is fine.

Kiwick · #5 11-28-2008, 06:47 PM

I once had a similar problem with a 90s Taiwanese 13" set, the yoke plug was faulty, just cut it off and solder the leads from the yoke directly on the chassis.

MRX37 · #6 11-28-2008, 07:12 PM

The yoke plug is fine, It fits snugly, all the connectors look fine, and the pins for it are firmly soldered onto the board.

radiotvnut · #7 11-28-2008, 09:21 PM

Was IC801 in your set mounted on a heatsink? The vertical IC should be mounted on a heatsink and you should be able to trace the vertical yoke windings back to it. Loose connections on the vertical IC are very common in all sets. Panasonics are also known to have loose connections on all higher wattage (1W and above) resistors.

MRX37 · #8 11-28-2008, 09:34 PM

No, IC801 was not attacked to a heatsink. Also, it's nowhere near the vertical circuit.

I've already resoldered a 5 pin STK IC, and everything around it. Every large solder connection on that board has been either touched up or resoldered, yet I'm no closer to solving this problem.

radiotvnut · #9 11-28-2008, 09:41 PM

The STK sounds like a power supply regulator or audio output IC. The vertical IC will be on a heatsink and the vertical windings on the yoke will trace back to it.

Geoff Bourquin · #10 11-28-2008, 09:58 PM

I haven't checked a service manual for your model, but it sure sounds like the vertical output IC needs to be resoldered. Most of these Panasonic sets use LA7838 for vertical output, although I have seen others on a few late models. The set will blank video as soon as it senses loss of vertical sweep; whack it just right and it may come back on.

MRX37 · #11 11-28-2008, 10:21 PM

Okay, I resoldered... something, and that fixed the unstable picture! It was a small connection, either to a small jumper or god knows what.

Now I just need to adjust the vertical height a tad, and I can be rid of this damn thing! Um... how do I adjust the vertical height...?

EDIT: The bottom of the picture looks fine, but the top is a bit too high. The scanlines are spaced farther apart at the top of the screen.

mbates14 · #12 11-29-2008, 12:01 AM

sounds like its time to ESR check caps now.

all that stuff is in the service menu/eeprom

MRX37 · #13 11-29-2008, 10:45 AM

Quote:

Originally Posted by mbates14

sounds like its time to ESR check caps now.

all that stuff is in the service menu/eeprom

Um, wouldn't a bad cap cause the vertical height to SHRINK? Also, why is only the top half of the screen affected?

radiotvnut · #14 11-29-2008, 01:27 PM

I've fixed many sets by replacing caps to fix the problem you describe.

MRX37 · #15 11-29-2008, 03:38 PM

Well, I replaced every cap around the vertical IC, and the problem is fixed. Ran the Tv for awhile and it's not doing anything funny, so I think I'm finally done with it!