New success: Banging TV brings picture back. Any insight?

Question

I made a post on the 6th about a new to me panasonic TV having a picture problem, with the picture fading out and back in. Thanks to all who replied. It's black video for the most part but I believe I found a way to bring the video back. If I bang moderately on the top of the TV (from above the glass to the back) I was able to successfully get the picture back three times within two minutes. Two times the picture faded right back out after a few seconds and the third time it's been on and perfect for about 10 minutes now. When it works then fades out, it fades out without being touched at all so it's not due to a physical problem like a loose item.

Does anyone have any thoughts? Does the banging on the top offer any new insight to the problem along with my other post? Again, there were no apaprent problems I could see inside regarding solder joints. I ensured that all the wiring connectors were securely plugged in.

What is my bloody problem with this! I can't throw it out because it clearly does work still! I just want to be able to get it to stay working!

Aloha Brian

Art · Accepted Answer

Mahalo! First there is a determined problem within the set, second, physical stress applied ocassionally causes the set to function, third, time to have a fellow from Hilo or Honolulu come over and diagnose the problem. Eventually the loose or broken connections within the set will fail and you will need to have service done, why not do it now before some catastrophic failure happens, or you hurt your hand? I personally would come over and check it out but your cost for air fare from the mainland would cost more than the set is worth. Aloha!

Ray · Answer

Brian, When someone says "fade" that usually implies it takes time for the picture to go away and come back rather than abruptly disappearing and reappearing. I would check the filaments of the picture tube to see if they darken as the picture goes away. If so, trace the wires from the CRT board down to the chassis to check or just resolder all the connections. CRT filaments are usually powered by the flyback. "Percussive diagnostics" shows you there is an intermittant connection. Next step: fix it.

Ray

Jumpster Jiver · Answer

It is probably a cold solder joint, tiny crack in a board or similar loose connection in the filament circuit. There should be 2 pins on the CRT marked "heater" or "filament" Follow these from the CRT to the board. Follow the traces on the boards to their source and all associated components. You may have to search with a magnifying glass or gently flex the board or tap components with an insulated prod such as a screwdriver handle with the power on. Be careful, be safe, and good luck

Tom MacIntyre · Answer

A lot of times the solder on the CRT board itself is pretty light, andprone to failure.Tom

James Sweet · Answer

It's obviously a solder joint, you haven't looked hard enough.

Brian · Answer

What would one look like? All the solders I've seen are perfect little dabs of solder. I re-soldered the 6 or 7 behind the filament two of which are for the heater with no success.Aloha!

b · Answer

look again. there will probably be some bad soldering somewhere, usually on the main board or one of the LOPTX pins.- try removing the crt neckboard and putting it back on again - could be the crt socket at fault.

Brian · Answer

Thanks guys. I checked the voltages behind each and every pin going to the filament and they are all getting their power which makes me think the problem as from the filament onward.

Is there a way to test the filament bulb itself? How about from the bulb onward?

Brian

Golf · Answer

Brian, I worked on a Hitachi that had a very similiar problem, andcould be temporarily fixed by smacking the set. I found a bad solderjoint on the horizontal driver transformer. This repaired it. Lookclosely at all solder joints. This particular joint had a hair linecrack in it. Good luck.

New success: Banging TV brings picture back. Any insight?

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