@pincoder Feels like I'm starting to get the hang of this... and then I find something new I don't understand
Last issue on the driver I'm having trouble with: special solenoids seem to work except for #6. When I ground 2J13-9 (via a jumper to 2J10 which is grounded against 2J8's grounding plate) I get no light up with the test LED connected to 2J12-9 and 5V. Mark's guide says I should walk the ground backwards through the components, presumably through 2J12-9 (which lights when I ground it directly).
Before 2J12-9 is an NPN (Q12 - TIP122). The collector seems to be getting flashed in the same rhythm as everything else in Leon's ROM, but I'm not seeing that flash on the emitter. The base appears to sit around 0.6V (according to my DMM, no oscilloscope here). The collector seems to be about 0.1V (but pulsing according to the logic probe). The emitter is about where the base is. None of them set off the test LED as being a valid ground. If I understand NPNs right, the 0.6V should be good enough to activate it and pull the collector (connected to 2J12-9) down to the solenoid ground. But I'm not seeing that, and even connecting the test LED directly to Q12's emitter doesn't seem ground-y enough for the LED. What gives?
Before that in the chain, the collector on Q11 shows dancing, but also doesn't light the led. It shows 5V on the collector, 0.06V on the emitter (which seems low enough it should light the LED?), and 0.25V on the base.
If I move back to IC 9, pin 13 doesn't do anything when grounded, 11 makes the flipper relay switch and 12 does nothing. 11 and 12 both show some dancing on the logic probe, but at different rates.
Here's one more thing I don't understand - if I ground 2J13-9 and put the test LED on 2J12-8, I get a very faint flash from the test LED. I don't know if that has anything to do with anything, but seemed funny.