Monitor condition

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PC updated by 18" Compaq PF 1141 monitor (year 2000)
mainly to enable screen setting 1024 x 768 dots (too small
on 16" screen) with ATI Radeon card under Win98SE.  This
worked fine until yesterday when
1.  Monitor made one soft pop noise
2.  Display enlarged momentarily i.e. all pixels flashed larger for
half a second, then back to normal.
3.  Normal since then.

Is this a pattern and what might it mean?
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)

Re: Monitor condition

Don Phillipson wrote:
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Probably a blown capacitor, most likely a bypass capacitor on one of the
power supply bus lines.  The flash was likely due to said capacitor
momentarily shorting as it blew.

There's a lot of redundant bypass capacitors in most electronics, so
that's why it's still working.

If it happens again, be prepared to fork out for a new LCD. You've
gotten 8 years out of that one, not too bad!

Re: Monitor condition

Don Phillipson wrote:
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If the display is a CRT, that is high voltage arc-over. On
my monitor, the arcing was on the surface of the flyback
transformer. And happened every 30 minutes to about 2 hours
of usage.

When the high voltage arcs over, the image will "bloom" for
a fraction of a second, until all the voltages stabilize

I used to run my monitor at 1280x1024, and by switching it
to a lower resolution and refresh rate, that was enough to
stop the arcing. Changing resolution and refresh rate, can
change the circuit conditions enough to stop the arcing.

Once a carbon trail forms on the surface where the arcing
is occurring, then it is easier for the next arc over to

For more information, talk to someone in a TV repair shop,
as they will have dealt with problems like that. Don't try
to fix it yourself, as your fix will likely be ineffective,
and there are lethal voltages inside the CRT cabinet.


Re: Monitor condition

Quoted text here. Click to load it

Thanks for clear and helpful reply

Don Phillipson
Carlsbad Springs
(Ottawa, Canada)

Re: Monitor condition

finger to keyboard and composed:

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I've seen corona discharge from the anode suction cap to the adjacent
aquadag coating on the CRT glass. This can give the same effect. You
can stop the arcing by cleaning any moisture from around the area and
applying some non-acid-curing silicone. Just be careful of any
residual electrostatic charge even after the monitor is powered off.

If the arcing is coming form the flyback transformer, then look for a
crack in the body. Colleagues have sometimes "repaired" such leaks by
drilling the cracks and filling them with silicone, but such fixes are
usually only temporary. If the arcing disappears when you change the
refresh rate, then this may involve switching to a different tuning
capacitor in the horizontal output stage. When these caps fail, they
usually go open, or low in value, which results in an increase in the
high voltage. Excessive EHT can cause arc-over at the anode cap or at
the focus grid in the CRT neck.

The following FAQ discusses EHT problems:

Snaps, crackles, and other HV breakdown

Arcing, sparking, or corona from CRT HV anode (red wire/suction cup)

Arcing at spark gaps and gas discharge tubes on CRT neck board or

Spark gaps and gas discharge bulbs on CRT neck board or elsewhere

Arcing from flyback or vicinity

Dave's complete procedure for repair of an arcing flyback

Arcing due to bad connections to or disconnected CRT return

Flashovers inside the CRT

- Franc Zabkar
Please remove one 'i' from my address when replying by email.

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