[PLUG] monitor flashing

[Denis Heidtmann]

On Thu, Oct 16, 2014 at 9:22 AM, Keith Lofstrom <keithl at gate.kl-ic.com> wrote:
> On Wed, Oct 15, 2014 at 12:14:37PM -0700, Denis Heidtmann wrote:
> ...
>> at a rapid rate--maybe 10 Hz.  After a number of seconds it becomes
>> steady.
> ...
>> Does this indicate that a complete failure is in  my near future?  A
>> power supply headed for a crash?  Things to test for?
>
> Sounds like the high voltage supply "squeeging" to me.  While you
> will probably end up replacing the monitor, you have a scientific
> mind, so learning cause and effect is important to your soul.
>
> The first experiment might be switching the monitor off and on
> after it has been running a while.  Do the same for the computer
> with the monitor on.  Which behavior rules?

The monitor's bad behavior occurs when it is powered on after being
off for "a while", where "a while" is poorly defined.

>
> Next, try warming the monitor up (perhaps with a heat lamp,
> or a few desk lamps) before turning it on.  We're starting
> into the cold season, and the daily moisture and temperature
> environment of the monitor has changed since summer.
>
> I had a monitor fail this way a few years ago, during the same
> season.  The explanation I came up with is that monitor power
> supplies have power transistor chips bonded to a metal base
> and encapsulated n plastic.  After a lot of temperature cycling,
> the plastic morphs a bit and the bond between plastic and metal
> develops cracks and voids.  When the power transistor is hot,
> the hot air in those voids will absorb more water vapor than
> the cold air around - moisture drifts into the voids in tiny
> quantities.  Cycle-cycle-cycle over years pumps in nanograms
> of water, which corrodes wirebonds and chip metallization.
>
> Another explanation is that the airspaces in the monitor fill
> with dust, the dust is hydroscopic, and moist dust adds too
> much electrical load to the high voltage.  So open it up and
> clean it out.
>
> Or perhaps an insect or spider crawled in there for warmth,
> and its carcass is now an undesirable electrical component.
> Ditto for the opening and cleaning.

Cleaning is certainly the easiest thing to do after opening it and
looking for burnt stuff.
>
> The Higher Purpose of failed electronic devices is an excuse for
> us to take them apart and learn about them.  Let us know what
> you find in there (besides high voltage - be careful!).
>
> Keith

Thanks for the suggestions.  I assume that the high voltage we are
speaking of drives some illumination--LEDs?

-Denis