Oh, damn, indeed the A1200 seems to have a 4 layer board. The corrosion wasn't so bad; but maybe there is more damage that can't be seen. Of course I'll need to double-check ALL the wiring of the floppy circuit :hammer:
The thing is that it broke suddenly while formatting a floppy, my guts are telling me that's some fault in the logic 
A shot in the dark, have you checked the power supply for voltage when you are accessing both drives? maybe it is failing.
