Just got a decent looking Black Knight pinball machine off craigslist. When I got it, it was blowing the solenoid fuse. Flexing the 40-pin inter-board connector appears to have fixed that, if only temporarily. Had the logic probe on it last night. Pretty pictures and verified that the CMOS is writing *something* (or something else is on the bus).
Here is an intro vid to the project, on "crappy-shaky-cam":
UPDATE: IT WORKS! The CMOS 5101 chip replacement fixed the problem!!!
(I put it in a socket just in case the new one blows)
Also, in the process of fixing this, I found a broken individual socket in the dreaded 40-pin inter-board connector. I bent the remaining metal in to contact the pin, but it will definitely need to be replaced sometimes soon. This may have been what was blowing the solenoid fuse. (I blew one first thing after putting the boards back - pressing on the 40-pin connector in places fixed it)
In addition, the sound board flakes out a bit and failed to come on after the fix. I wiggled some connectors, and it started working again. Lots of connector cleaning will need to be done, but at least I know the game *works*!
Jeri Ellsworth mentioned to me that the audio buzzing on start-up may mean capacitor problems. The buzz goes away as the machine warms up, which she said even more so means cap problems. I can see that the power supply caps appear to be original, and if so, they're 30 years old now; way past their prime.
(thanks Jeri for the pin-fixing advice, and thanks to all the folks out there who have posted info about fixing pins, especially here