Entertainment Center: TVs, Stereos, VCRs and DVDs - Panasonic 27" screen gets dark after 5 minutes

Hi, I have a Panasonic 27" TV (Product Number CT-27G24A). It powers up fine and works great for about 5-10 minutes. Then suddenly the pictures gets very, very dark and out of sync - the overall picture is moved like 10" up, even the onscreen setup menu now appears on the top of the screen as well, while it usually shows up on the bottom. If I turn the set off and let it cool down, it will work again for about 5 minutes.

What could cause this? And is it work worth fixing it?

I adjusted the 'Screen' (or G2) potentiometer slightly - to make the picture appear a bit brighter. Now the problem with the screen being out of sync and dark is gone.

Can someone comment if this will be a permanent fix? Or can this slight adjustment of G2 lead to a bunch of other problems, and should I change it back and continue troubleshooting...? Thanks.

Most likely it wont be a permanent fix. Something has to be causing the flyback to underpower the tube. usually the screen just gets dark though. The flybacks output power usualy doesnt affect the image positioning. To me it sounds like something in the horizontal deflection circuit. The main part of the circuit is a transistor about 1200V 5A, in newer sets it looks like black square with three protruding legs mounted on a heat sink. in older sets it usualy looks like a short silver cylindrical piece of metal mounted in the middle of the heatsink. This circuit is usualy near the flyback transformer. i suggest checking this curuit. also it could be some of the high voltage capacitors near the flyback. pay special attention to the ones with the 1Kv and over voltage rateing. make sure you short the capacitor leads though as they can contain lethal voltages.
NOTE FOR SAFETY: IF YOU ARE NOT EXPERIANCED IN TV REPAIR DO NOT ATTEMPT WHAT I HAVE JUST TOLD YOU, UNLESS YOU HAVE SOME KNOWLAGE OF ELECTRINICS. THE VOLTAGES INSIDE TVS CAN EASILY EXCEED OVER 60,000 VOLTS!

NOTE FOR FUTURE REFERANCE: Most image distorting affects such as shadowing, visible scan lines, flickering, or a jumpy image are most likely due to dead or poor electrolytic capacitors.

Looks like you may have a vidio problem. If the HV was low picture would be dim and possibley out of focus. I'd leave the flyback alone. Also does this set have PIP. If so the board with the PIP is a good canidate for trouble. Terahertz? have you ever been in a Tv before? I've got over 30 yrs experiance. leave it to the pros.

Thanks for all the help.

Yes, this TV has PIP. How can I easily troubleshoot the PIP board? What should I be testing first, capacitors, transistors, etc. - any suggestions?

Thanks again...

First thing to get a hold of in equipment is a good ESR meter to check the electrolytic caps on the PIP module. If their the small silver surface mounts their prone to go bad. The ESR meter will help alot. If any cap checks dry you can replace it with a standard electrolytic cap. You may also isolate by using frost mist on the caps. when the pic goes dim, start spraying the caps on the PIP module very slowly. You might get lucky.