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

[Brian]

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]

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]

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.

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]

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

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]

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

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

Tom

 

[James Sweet]

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!

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

 

[Brian]

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]

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.

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]

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]

Brian, I worked on a Hitachi that had a very similiar problem, and
could be temporarily fixed by smacking the set. I found a bad solder
joint on the horizontal driver transformer. This repaired it. Look
closely at all solder joints. This particular joint had a hair line
crack in it. Good luck.