WG6100 deflection board madness

ARGH! The "Guess Who's Coming For Dinner" bug killed my WG6100.
(You know, the fact that saying "hey, I've got a friend in from
out of town, I'll show him my Tempest machine!" immediately causes
hardware failure...)

Symptoms: Vectors clatter, no picture, spot killer on.

Quick fix: Tap heatsink on Q603. Picture comes back.

Obvious cause: Cold solder joints on Q603. Confirmed visually.

Long fix: Resolder joints on Q603.

Symptoms: As above. Fixing the problem killed the monitor.

Probing around reveals:
- Y amplification is fscked.
  - Pins 3 and 6 of J600 (Y) show a constant voltage.
  - Pins 3 and 6 of J700 (X) show a varying voltage.
  - I have good voltages on either end of R608 and R603, and
    ditto for pins 7 and 7 of J600, so it looks like all the
    power is getting to where it's supposed to.
  - Testing further in-circuit is damn near impossible due to
    the geometry of the probes and the deflection board in the
    monitor.

Out-of-circuit testing:
- Q603 and D602 appear to be good.
  - WTF !?!?

What else could be wrong?

-=+=-

As long as we're on the subject, I also have a deflection board
that eats deflection transistors. When last powered up a couple
of years ago, the symptoms were that it displayed a picture for
a few seconds and then promptly cut out half the X-side of the
screen and blew some deflection transistors. I gave up fixing this one
when I swapped it out for my Y-amplification-buggered board. Sigh...

Anyone seen behavior like either of these before? I'm at wit's end!

Later,
Doug.

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