Threw a few more hours at the A2000 today, cleaning up here and there. I popped out the 68000, cleaned up the pins, and checked the socket. The socket wipers are immaculate, not a speck of corrosion or acid on them (I checked with a magnifying glass). The pins for the socket on the underside of the board are still nice and shiny, so I’m willing to say the socket is alright.
The CPU pins 1 & 2 (which I think are address lines? Need to GIS the pinout) were pretty corroded both inside and outside above the wiper line. I brushed them with the fibreglass pen until they were better.
Putting it back in, I noticed that some traces around the resistor nets have some black spots, which I think are corrosion. I multi’d out the resistor nets, which are ‘mostly’ in spec, with one pin on one net and two pins on the other net that seem to have much lower resistance than they should.
Look to the top right of the RP900 silkscreen, between pins n-4 and n-5 of the false resnet. Excuse the generally greasy appearance, because I was scrubbing this with alcohol to see if it was just dirt.
Since I was getting bored, and figured I might as well see if anything works, I plugged in the power supply and fired it up. As expected, it won’t boot normally (goes to the white screen, which I think indicates CPU failure.)
After a bit of fiddling, I tore the machine apart and performed the work I should have done before anything else: resocketed some chips. Still white screen.
I put the ‘030 CPU card in, and booted it up. It went grey, light grey, white screen, and then to the Workbench 1.3 “insert disk” screen.
So some progress today. I don’t actually have any disks for this thing, and eBay only has 2.x+ Workbench disks, so I’ll have to take out the A500 or something and send enough stuff at it to make a floppy from an ADF.
Update: I came back a few days later with an intent to thoroughly follow the schematics and figure out just what isn’t working.
After doing continuity testing around the CPU bus, I determined that some of the pins (D2, D3) on the 68000 did not have continuity to their own socket. This is no doubt the cause of the problem, and so I have relegated myself to desoldering and replacing the entire 68K socket.