I have a SuperVGA monitor that won't keep its focus. If I focus
it when I first turn it on, it slowly goes out of focus as it warms
up. If I try to keep it in focus as it warms up, I can keep it in
focus, but some of the other adjustments peak out (like horizontal
and vertical size) What is wrong with it?
This was a question posed on the Classic Computers mailing list.
Whilst it is not specifically Amiga-related it may still be a
problem for Amiga users who use an VGA or SVGA display such as
those with a graphics card. I make no guarantee that this will
work, it is just a suggestion on the problem.
It is possibly a high-voltage problem. In most monitors the
focus supply (5kV or thereabouts) comes from
the flyback. As does the EHT to the CRT. And the EHT voltage does
affect the size of the picture (higher EHT -> `stiffer' beam
-> smaller picture for a given deflection field). Try to find
the supply to the horizontal output stage, this is probably around
150V. Having a service manual helps. If that drifts as the monitor
warms up, then debug the power supply. If it's steady, it is likely
a problem with the divider network in the flyback. To find more
information visit http://www.repairfaq.org/~filipg/
for additional help.
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