"Cobalt" wrote in message
news
a lot of monitors have a small trimpot neat the fbt that sets the
overvoltage trip point - it could need a tweak.
there is also sometimes another trimpot nearby to adjust the hv output ,
this could also simply need a tweak.

whenever you tweak a pot, mark the original position with a sharpie so you
can align it back to the original position in case you adjust the wrong
one.


I wish it were that simple, but there are no pots on the PCB at all. All
there are is a lot of power transistors on heat sinks and many smaller
components, but nothing adjustable.
The problem occurs both hot and cold (at startup as well as after running
for several days non-stop.) I can't seem to locate it with hot/cold
application and it occurs too infrequently to reliably track down. But most
frequently, it occurs after coming out of standby mode. I had been using it
non stop for months after I disabled Windows standby for the monitor,
leaving the monitor in operating mode 24/7. But the problem started to
appear again this spring, even when not using standby features, so I'm
forced to deal with it now.

Couple of options:

I could put the FB back in the "replacement" monitor's motherboard and put
that it this monitor (mine is much newer than the "replacement" and MUCH
cleaner--like new in fact) and hope that no components on the older board
are worn or impending failure.
Thinking about the ringing problem in the video on the 'replacement' unit,
it may be confined to the module that contains the DB15 connector. It has
the RGB drive outs that feed the circuit board on the back of the tube.
Perhaps that module on the "replacement" monitor is poorly-compensated for
overshoot and if I use my input module, would still result in a good quality
display. (NEC did improve the video amplifier circuits after June 2000,
apparently, as my other two newer AS120's don't have the overshoot/ghost
images around small text and the overall display is sharper, more like an
LCD.)
Hopefully the motherboard has nothing to do with the ringing/text quality
and I can just replace it.

Other option is to change all the power transistors for the ones in the
"replacement" board. But the cycle of testing and the sheer amount of labor
(40-50 screws, & 2 hrs labor) to disassemble and swap a few transistor and
then test again, might be more than reasonable.

But the problem occurs more frequently when the monitor uses Standby and
comes out of standby, than if I just leave it running with no standby. There
has to be an answer in there somewhere....

--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
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