Star Wars 25 inch Amplifone issue

The monitor on our Star Wars sit down machine at work is having issues. It
started with an intermittent issue where the screen would suddenly turn green,
and it was very bright and all the retrace lines were showing, and all the lines
were out of focus. Smacking the cabinet would sometimes bring back a good
picture. Then we also lost vertical deflection, so we opened it up to take a look.

The deflection issue was easy to fix. We replaced a few transistors, and a
fuse, and it was working again. The other issue we're still struggling with, in
fact it's much worse, and is mostly in the bad state, with occasional flickers
of it working correctly.

We initially thought it was a bad connection in the CRT socket, as it seemed to
change as I was poking the socket with a wooden stick. So I replaced the CRT
socket harness with a spare one I had. That didn't work. So poked some more,
and started to think there was a loose connection in the focus block. But then
poking further didn't do anything.

So, we started to suspect that something is just randomly working for short
moments, and whatever I was poking when that happened made me think that was the
issue.

We are now wondering if maybe the green drive transistor is shorted on? That
would explain everything looking green, and the retrace lines, and the
brightness. Would that also explain the poor focus?

Any other suggestions?

Thanks!

___
Ken
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Received on Wed Sep 11 19:09:54 2013