I found a 2nd (mostly) working Classic on eBay, and have been able to narrow things down by swapping components.

What I have learned:

- The analog board and screen are working perfectly. I tested the voltages from the analog board and they were right on. I can get to a sad mac if I press the programmers interrupt button. And if I swap the logic board with the newer board from eBay, It boots to the desktop.

- The ROM is fine. I swapped ROM between the working and broken logic boards. The working board continued working, the broken board continued broke.

- The RAM expansion card is working perfectly. As is the disk and floppy drive.

In poking around I did find one trace where there is a very clear and obvious run from a chip pin to a via, but no continuity measured between the two. The connection looks perfect to the eye, but not to the ohm meter. In light of this, I think my next step will be to reflow the board in an oven. I've never done this before, but it sounds fun