17 Apr
2008
17 Apr
'08
2:30 p.m.
The two faults I remember with VT220 terminals were
dead 9636/9737
EIA chips, and loss of horizontal hold. It was tough getting the
old EIA chips out to mount sockets (must have had heavy copper
inner layers on the mainboard PCB), but once that was done, those
were easy to fix. We only lost about one a year, anyway. The
video, I was never able to fix myself with what I knew then. Perhaps
I could fix it now.
I've had to repair a few VT220s with no horizontal hold. It seems to be
due to bad contact at the horizontal hold preset. Pull the case, note the
positon of this preset, and turn it from end to end a few times, finally
putting it back to the original postion. Power up and most likely the
picture will be locked. If it is, put the case back on.
-tony