If you have tried a known working floppy drive, you might want to try
another cable as well, sometimes these can go faulty.
Failing that, it's possibly a motherboard problem, either with Paula,
which handles read/write data, or one of the CIAs which handle disk
control signals.
There's other discrete logic in the circuit as well, but generally
this is fairly reliable.
Parts can be easily obtained from a dead A600 or A1200. You just need
to learn SMD soldering, to take it to someone who knows.
Anthony.
