What causes this kind of failure in a CRT monitor?

S

Slater

Guest
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:
http://www.youtube.com/watch?v=GaP2Bv5nCaQ
It hadn't been used for many months or maybe years.
What happened?
 
Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

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.
Click to expand...
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.
 
Slater wrote:

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:
http://www.youtube.com/watch?v=GaP2Bv5nCaQ
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.
Click to expand...

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
 
Slater wrote:

Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


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.
That's another possibility.
Click to expand...

Jamie
 
Slater wrote:
Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

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.
Click to expand...
If the flicker problem changes when you turn the vertical hold or
linearity controls that would indicate a pot problem.

Have you tried control cleaner such as MG's Tuner Lube? About the only
way to restore potentiometers...

Otherwise it could possibly be HV leakage - take the rear cover off and
turn it on in a dark room to see if there is any arcing. You would
likely hear some sizzling noise too and smell ozone if there is a HV leak.

John :-#)#

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"Slater" <nontelo@dico.no> wrote in message
news:4d99a15c.603015@powernews.libero.it...
It's doing that thing again. DAMN!!!!
Click to expand...
I know what happened.... You plugged tab A into slot D didn't you.
 
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:
http://www.youtube.com/watch?v=GaP2Bv5nCaQ It hadn't been used for
many months or maybe years. What happened?
Click to expand...
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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