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What causes this kind of failure in a CRT monitor?

S

Slater

Jan 1, 1970
0
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?
 
S

Slater

Jan 1, 1970
0
Jamie said:
That looks like HV leaking somewhere. You may also have some
cracked insulation in the Anode lead or flyback coil. You could
even have a cracked solder joint or moisture in it.

Thank you very much for your advice. It's not doing that anymore. It
looks like some oxide or dirt is present in the vertical size
regulation knob, although I'm not 100% sure.
 
J

Jamie

Jan 1, 1970
0
Slater said:
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?
take it apart, clean out the dust in it for one thing.

That looks like HV leaking somewhere. You may also have some
cracked insulation in the Anode lead or flyback coil. You could
even have a cracked solder joint or moisture in it.

Jamie
 
J

Jamie

Jan 1, 1970
0
Slater said:
Thank you very much for your advice. It's not doing that anymore. It
looks like some oxide or dirt is present in the vertical size
regulation knob, although I'm not 100% sure.
That's another possibility.

Jamie
 
S

Shaun

Jan 1, 1970
0
Slater said:
It's doing that thing again. DAMN!!!!

I know what happened.... You plugged tab A into slot D didn't you.
 
R

Ray Carlsen

Jan 1, 1970
0
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
 
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