On Thu, Oct 16, 2014 at 9:22 AM, Keith Lofstrom <[email protected]> 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 _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
