My remark about working plug-ins turns out to have been prophetic rather than merely sarcastic: the 7B53A that I obtained "for parts, not working" is, in fact, not working. The big daughter board (670-1864) is dirty and badly corroded along the top inter-board connectors, and the corrosion is also present on the main board ((670-2257) along the mating pins for the same connectors. It's actually some of the worst damage I've seen in a scope so far, and that includes a 5103N that was literally filled with dog food. I'd even say that this is worse than the 5103N that arrived with the CRT shattered in shipment.
I verified that the horizontal plug-in was not working by tracing back from the vertical deflection pins on the CRT through the vertical amplifier.
At the moment that only leaves me with the 7B53A that came with the 7623A, which had suffered some severe kinetic trauma. I could probably rebuild that unit with parts from this one (or vice versa), but I've already got another horizontal plug-in on the way (as part of an entire scope that is known to be working). I may still try to disassemble this 7B53A and see if a) the damage is as severe on the main board, and b) if I can make one working 7B53A from two damaged ones.
I could also put one of the vertical amps in the horizontal bay and feed it a sawtooth. It's worth a try, at least.
It does not feel like it, but I think that this is progress.
-- Jeff Dutky
