frog said:
Has anyone experienced this fault on a CRT monitor - a 4 yr old LG
Studioworks.
Once or twice a session the display momentarily has a fit! The image dulls,
appears to zoom out of the screen and then contracts back to normal size and
brightness. This happens in a split second and there is also a 'crackle'.
It started happening once every several hours but the freqency is
increasing.
If this is a known but cheaply fixed fault fine. Otherwise I'm loathe to lay
out $X only to be told that it'll cost $Y to fix which might be a good part
of the cost of a new monitor.
F
The sound could be related to high voltage arcing inside the monitor.
When it happened to my CRT, a temporary solution was to reduce the
resolution and refresh rate. There is some relationship between
resolution and refresh rate, and the voltage level on the high voltage
wiring and circuits.
For example, if you are at 1280x1024 at 85Hz, try 1024x768 at 60Hz. Then
see if the monitor arcs.
In my case, there seemed to be arcing over the surface of the flyback
transformer. With some materials, a "carbon track" will develop, and
that forms a conducting path which is hard to correct. If a component
has burn marks or pin holes in some insulation, then perhaps it should
be replaced. There are also materials that can be used to apply external
insulation in a high voltage circuit, but using them is useless if
the surface of the component is already compromised (burned).
A TV repair shop may be able to look at it for you, and give you some
idea which component needs to be replaced. If I thought I'd be able to
get replacements parts (a new flyback), I might have had mine fixed.
I just retired it instead, and switched to an LCD (which is not as nice
in some respects). Doing so, means I went from wasting 200W power in
the CRT, to less than 36W for the 17" LCD.
There are other failure mechanisms that can lead to the arcing sound.
For example, a CRT design may have circuit features, to prevent the
tube voltage from going too high. If the voltage becomes high
enough, the tube can emit x-rays, so safety features are added
to protect against that kind of failure (too high a voltage). Not all
arcing sounds are caused by surface arcing on high voltage components,
but may be caused by a safety feature.
Paul