ACTUAL SUCCESS!
First I traced the INTENSITY control signal through the logic board, and checked Q90, Q108, and U99 (a C3046 transistor array). All of those checked out fine. Then I traced the gate signal from the logic board, through the main interface board, and to the Z-axis amp (it seems that I am fated to fix Z-axis amps). Once at the Z-axis amp I verified that the gate signal coincided with the signal I was triggering against (the front panel probe calibration signal) and then simply checked every transistor on the Z-axis board using my trusty component tester.
I found that Q1148 was bad. That's just a 2N3906, which I have plenty of, and replacing that brought traces to the CRT! Easy as pie.
I was also able to fully rejuvenate the INTENSITY pot by dripping Faderlube down the internal shafts of each pot section. I was never able to figure out how to get the pot sections open to clean the wiper and track, but that doesn't not seem to matter, as the Faderlube seems to have done the trick: the intensity pots are much smoother, and there's not more scratchiness or dead spots. I also applied DeoxIT to the switch at the end of the mod pot, which also helped make the switch action smoother and crisper.
Now it's on to "removing" Option 1 (aka installing a readout board). I have readout board, and the necessary Peltola cables, I just need to make the ribbon cables. I am studying the schematics so that I'm sure I understand all the connections that are needed.
It's a pretty good deal, getting a working 7603 for the price of two transistors (the PN2907A and the 2N3906).
-- Jeff Dutky
