I bought a Macintosh Classic sometime early pandemic for nostalgia. I got a terminal emulator loaded up and connected to a Raspberry Pi, so I use it for writing or browsing the small web.
A few weeks ago, I started getting gray, horizontal lines on boot. I opened it up- and the mainboard on this thing is so strange. There's the main board with ports and what looks like a processor- then *another* board of similar size with another with a Motorola chip and RAM. The two boards are only mounted together by a socket that overlaps the processor, and very flimsy.
Whatever, it was 1991, they did 1991 things...
All signs online pointed to a bad capacitor, so I tried washing the board with alcohol, but no luck, and I don't really want to recap it. And the top board is so difficult to clip back on.
On a lark, I decided to just plug the main board with plugs and not the second board... and it booted right up!
It turns out this second board is 40MHZ expansion card! Pretty rare! I'm not sure it was ever working, but a neat find!