Hi,

I'm having a problem with my Optiquest Z90 monitor - Model#
VCDTS21603-1M.

Q442 is being blown out almost instantly on power up. Nothing else
appears to be wrong. No obvious burned parts, and no loose solder
joints that I could find. I traced the leads from Q442 back and tested
what I could along that path, everything seemed to check out.

I'm wondering if anybody is familiar with this model and could tell me
what may cause this, or at least what Q442 does, or can point me to a
schematic. I have had zero luck searching for this model online.

This is a last ditch effort before I junk the monitor, which would be
a shame because otherwise it was a pretty nice one.

Thanks in advance

What is the function of Q442 ???
Does this set use a separate circuit for the high-voltage and
the horizontal sweep ????

On many sets, an FET transistor is used to regulate the voltage
going to the Horizontal output transistor (HOT) and the sweep
driver transistors. If these short, it will usually blow the transitor
it is supplying. Also check the electrolytic capacitor and the diodes
that are part of these regulator circuits.
Hope these help...
John