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Intermittient problem with TV

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

Reply to
Tube Audio
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Get the cover off, turn the set on, and tap on the set to get the 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.

Reply to
tnom

Look for bad solder joints at the vertical output IC.

Leonard

Reply to
Leonard Caillouet

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.

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Blattus Slafaly  ? 3     :)  7/8
Reply to
Blattus Slafaly

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.

Reply to
Ancient_Hacker

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.

Reply to
Tube Audio

On Oct 5, 10:46=A0pm, "Tube Audio" wrote: [about a TV that goes dark]

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.

Reply to
whit3rd

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