Intermittient problem with TV

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.

Look for bad solder joints at the vertical output IC.

Leonard

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.

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.

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.