Richard Rasker wrote:
Op Wed, 22 Nov 2006 08:14:56 -0800, schreef herb_k:

This computer monitor will show a momentary, thin horizontal glitch
shoot across the screen. This happens a few times per hour. For several
weeks now, and occurring about once every couple of days, the screen
will suddenly go completely black. When that happens, I turn it off for
an hour or so and then it will function okay again. The occurrence of
the blacking-out is getting more frequent. It now happens 2-3 times a
day.

What would be the likely cause? Thanks.

This sounds like bad solder joints, most probably in the horizontal or
vertical deflection circuitry. Inspect the pcb's solder side, and in
particular larger components (coils, connectors, TO220 transistors), and
components attached to a heat sink. Look for a sort of "crater ring"
around component pins; here's a clear example:
http://www.linetec.nl/electronics/badsolder2.jpg

Hope this helps, regards,


Richard Rasker


absolutely right, it helps

After reading Richard's reply, I figured that when the screen blacked
out again, I could whack the case. That repeatedly brought the raster
back in the following days, and also indicated the loose connection.
Today, I finally opened up everything and examined the circuit board.
After a long time looking, I found a solder joint looking just like the
ones in Richard's example photo. It was underneath the transformer.

It was surprsingly easy to melt the existing solder. Some got wicked up
inside the hole, which seemed good. I also added some more solder. When
I reassembled and reconnected, I had to adjust horizontal and vertical
size and position - so that tells me I probably have indeed resoldered
the right connection. Raster is now stable so far, too.

It feels really good to repair something and have it all go well.
You've got to love this group Merry Christmas, everybody.