"Nomen Nescio" wrote in message
...
My 6 year old Viewsonic PT775 occasionally loses vertical deflection for
just the top half of the CRT. What happens is a very bright horizontal
trace appears exactly midpoint across the screen, the top half is gone,
and the image below is normal. Is this a yoke problem or something on a
PCB? I wasn't aware that there might be circuits controlling upper and
lower vertical deflection, but that's what appears to be happening.

Of course this is an intermittent problem. Right now I'm using the thing
and it's working fine. An hour ago it did what I described above. Was
getting ready to take the back off (again) and wiggle some wires around
the yoke, all in the hope of finding some loose connection. No such luck
though, as now it's working perfectly normal. I can't seem to induce or
reproduce the problem. Just happens on its own. If I should be lucky
enough such that it fails continually as I described, what would be the
areas to investigate?


Stop using it immediately before you damage the CRT. Find the vertical
output chip, it should be on the main circuit board bolted to a little
heatsink, it'll have 6-12 pins on it, resolder those pins and the monitor
should be back to normal. Chances are you'll see visible cracks in the
solder around the pins.