Intermittient problem with TV

T

Tube Audio

Guest
I have a 27" crt Panasonic TV.

Sometimes the picture goes out, the screen goes black. The sound is still
there. A few minutes later it might come back.

Sometimes if you tap on the side or top of the tv the picture comes back.

This has been happening for a few months and has seem to happen more often.


I am thinking it is a cold solder joint and I was thinking of removing the
back of the tv and resoldering some of the connections.

I know about discharging the crt to avoid shock hazard.

What are of the tv circuitry should I focus on re soldering? The area that
has the caps for the Horizontal Output Transformer? The video area? The
small pc board on the back of the crt?

Any ideas would help. I have a feeling that it is a cold solder joint and
not a worn component , but I may be wrong.

Thanks
 
"Tube Audio" <tubeaudio@sbcglobal.net> wrote in message
news:3W4Gk.3912$be.3162@nlpi061.nbdc.sbc.com...
I have a 27" crt Panasonic TV.

Sometimes the picture goes out, the screen goes black. The sound is still
there. A few minutes later it might come back.

Sometimes if you tap on the side or top of the tv the picture comes back.

This has been happening for a few months and has seem to happen more
often.


I am thinking it is a cold solder joint and I was thinking of removing the
back of the tv and resoldering some of the connections.

I know about discharging the crt to avoid shock hazard.

What are of the tv circuitry should I focus on re soldering? The area
that has the caps for the Horizontal Output Transformer? The video area?
The small pc board on the back of the crt?

Any ideas would help. I have a feeling that it is a cold solder joint and
not a worn component , but I may be wrong.

Thanks
Click to expand...
Look for bad solder joints at the vertical output IC.

Leonard
 
Tube Audio wrote:
I have a 27" crt Panasonic TV.

Sometimes the picture goes out, the screen goes black. The sound is still
there. A few minutes later it might come back.

Sometimes if you tap on the side or top of the tv the picture comes back.

This has been happening for a few months and has seem to happen more often.


I am thinking it is a cold solder joint and I was thinking of removing the
back of the tv and resoldering some of the connections.

I know about discharging the crt to avoid shock hazard.

What are of the tv circuitry should I focus on re soldering? The area that
has the caps for the Horizontal Output Transformer? The video area? The
small pc board on the back of the crt?

Any ideas would help. I have a feeling that it is a cold solder joint and
not a worn component , but I may be wrong.

Thanks
Click to expand...
Glue a solenoid to the back of it that you can activate by remote
control. Every time it goes blank, hit the solenoid and it will jar it
back on.

--
Blattus Slafaly ? 3 :) 7/8
 
If the picture slowly fades away over ten seconds or so, it's a
intermittent heater connection at the crt base socket.

If it's sudden, then it's probably a poorly soldered connection, or a
cracked component.

Then again, it could be most anything.
 
Hi

I just took the back off and I think I found the vertical output ic.


Would it be LA7838, the vertical deflection circuit with TV / CRT display
drive IC?

THere are a bunch of caps around it too. Time to turn on the soldering
iron.



"Leonard Caillouet" <nospam@noway.com> wrote in message
news:8B7Gk.6466$_G.4947@newsfe04.iad...
"Tube Audio" <tubeaudio@sbcglobal.net> wrote in message
news:3W4Gk.3912$be.3162@nlpi061.nbdc.sbc.com...
I have a 27" crt Panasonic TV.

Sometimes the picture goes out, the screen goes black. The sound is
still there. A few minutes later it might come back.

Sometimes if you tap on the side or top of the tv the picture comes back.

This has been happening for a few months and has seem to happen more
often.


I am thinking it is a cold solder joint and I was thinking of removing
the back of the tv and resoldering some of the connections.

I know about discharging the crt to avoid shock hazard.

What are of the tv circuitry should I focus on re soldering? The area
that has the caps for the Horizontal Output Transformer? The video area?
The small pc board on the back of the crt?

Any ideas would help. I have a feeling that it is a cold solder joint
and not a worn component , but I may be wrong.

Thanks

Look for bad solder joints at the vertical output IC.

Leonard
Click to expand...
 
On Oct 5, 10:46 pm, "Tube Audio" <tubeau...@sbcglobal.net> wrote:
[about a TV that goes dark]
I just took the back off and I think I found the vertical output ic.

Would it be LA7838, the vertical deflection circuit with TV / CRT display
drive IC?
Click to expand...
Look for solder joints that have visible cracks, especially around
connectors (the CRT tube-base connector for one, and the
wiring connections that go to that circuit board). Look also at the
heavy pins of power semiconductors and capacitors, and
the flyback transformer. Those heavy conductors are
most likely candidates for an insufficient-heat 'cold' solder
joint.

Dark screen can result from filament or screen connections to
the picture tube, or any of the high-voltage parts that generate
the high anode voltage. Intermittent connections are easily probed
with a (for instance) bamboo chopstick if you can open the
set up while it's operating.
 
On Sun, 5 Oct 2008 08:19:27 -0700, "Tube Audio"
<tubeaudio@sbcglobal.net> wrote:

I have a 27" crt Panasonic TV.

Sometimes the picture goes out, the screen goes black. The sound is still
there. A few minutes later it might come back.

Sometimes if you tap on the side or top of the tv the picture comes back.

This has been happening for a few months and has seem to happen more often.


I am thinking it is a cold solder joint and I was thinking of removing the
back of the tv and resoldering some of the connections.

I know about discharging the crt to avoid shock hazard.

What are of the tv circuitry should I focus on re soldering? The area that
has the caps for the Horizontal Output Transformer? The video area? The
small pc board on the back of the crt?

Any ideas would help. I have a feeling that it is a cold solder joint and
not a worn component , but I may be wrong.

Thanks

Get the cover off, turn the set on, and tap on the set to get the
Click to expand...
intermittent behavior. Do this in complete darkness. Locate the area
of sparking and then turn your flashlight on to exact the location
of the bad solder/connector joint.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top