UPDATE: No joy. Still self-reboots.
So, I put the Merlin II card back into the XL1201, connected the power and console, and powered it up.
Nothing. Blank screen (which means the monitor was at least getting a signal) but no boot, nothing. I hit the reset button a few times and powered it off and on a few times, and tried to reseat the card. Not a thing.
So, removed the Merlin II and took a very close look at it, comparing my before pictures to everything, to make sure every chip was in the right place and every pin was in its slot.
Sure enough, I found exactly two chips inserted incorrectly - backward. Of course, they were the only two "vertical" chips, in locations FF1 and FF4. I removed, reversed and reseated them, and the XL1201 powered on and booted into Genera like a champ.
This was at 5:12PM. If I fixed things, it will still be running at, say, 5:42PM or even overnight. If I didn't, I would expect it to crash or reboot itself sometime between 5:27 and 5:32PM.
I guess we'll see...
Wait a while...
Well, it self-rebooted at 5:44PM. I guess I will do the same thing on the Merlin I/O board another weekend and we'll see what happens from there.
- Remove, clean, reseat all DIPs in the Merlin I/O card
- Possibly remove, clean and reseat all PGA, PLCC and other challenging chips
- Install a heat sink on Ivory CPU?
If those things don't work, then:
- Replace broken capacitor on Merlin II CPU card
- Replace all axial tantalum capacitors on the two boards and the backplane. Perhaps start with the backplane as it's small.