Hello, I have a Commodore 15KHz monitor that I tried to use as a TV
set by attaching it to my decoder through a SCART lead. It worked
perfectly for a while, then it started doing this:
It hadn't been used for
many months or maybe years. What happened?
Slater,
Those monitors, mostly made by NAP (Philips), were notorious for
intermittents of all kinds caused by bad solder joints. When I get one
of those beauties on the bench, the first thing I do is go over the main
(and CRT) board and resolder all suspicious connections, then check for
any other problems, if any. Pay particular attention to the flyback
(LOPT) and H driver transformer, all power transistors, IC's and diodes,
and all resistors of 1 watt and larger... essentially anything that
generates heat. The movement of component leads via heating and cooling
in normal operation eventually causes the solder joints to break loose.
I'll bet your vertical sweep problem is caused by bad solder. Solder
problems can show up when the monitor is cold but go away as it warms
up... or vice-versa.
Be careful when you pull that bottom metal plate off the PC board.
It's soldered all the way around and unless desoldered carefully, you
can damage the grounding traces. Good hunting!
Ray