Black Screen with horizontal white line in center on Panasonic CT-27G24A?

In my case, the black screen with horizontal white line does not happen all the time. It only happens after the TV running for ~30 mins - 2 hrs.

I inspected the solder points around the vertical sweep circuit, and did not see any cracks.

I suspected it is a failure of the vertical sweep circuit or the heat compensation resistor for it.

Any suggestion? Thanks.

lazi boy
August 2010

Sound like a intermitent vertical sweep circuit
(aka vertical deflection) failure. The transister
at one of it's solder points is loose and not soldered well. You could look carfully and try to resolder the old
transister, or just try to resolder
and new transister in there.

DJ Frankee Cee
March 2010

Sam, I am having the same exact problem with my Panasonic CT-27G3W. Were you able to fix it by yourself? Can you please tell me how to fix it? Is it easy? Or should I look for some TV engineer?

Pam
September 2007

Hi Sam.

You need to look around the frame output area. The circuit board may be marked, but probably will not be.

Basically, you need to inspect the soldered joints for a hairline crack where the leg of the component has passed through the board. It is more likely to be on a larger joint, although they can occur on smaller ones too.

I am not familiar with USA models (as I assume yours is), being in Europe so I do not know if your tv has a frame output that consists of transistors of of an IC, but the component(s) you are looking for are likely to be fitted with an heatsink.

You could also try resoldering the joints on the flyback transformer, -the item with the thick EHT - (Extra High Tension, or voltage) cable emerging from it and going to the CRT. Be careful around any of the insides of a TV if you are not au fait with the workings. Even with the mains plug disconnected at the wall, the CRT will still store a charge of around 25'000 volts for many days.

If in doubt, have it looked at by a TV engineer. As I said before, it should not be expensive..... and your life is probably worth the cost!!

Good luck.

Lee
August 2007

Hi Lee,

Thank you for your reply. Do you know any possible places to look for the dry joints? I've just read a little about this and something called vertical deflection lost. If it is simple soldering, I can do this myself. Thanks.

Sam
July 2007

That effect is called 'frame collapse' (or 'field collapse'). The fact that pressing on the AV connector restores normal operation is not in itself significant, but it does suggest there is a dry joint, (broken solder joint) in the frame circuit area. The pressing of the AV connector is transferring movement to the broken joint and bringing it back together, hence it works again properly.

This should not be an expensive job to have done by a TV engineer.

Lee
July 2007