It's essentially the same as the first one I posted. So I guess the poor MK2's cable was hurt, the IDE circuitry has a problem, and the DSP has a problem.

The only odd bit is a resistor soldered in to the right of the IDE header. Maybe this is the fix for the very dim display which Stu applied recently. The MK2 worked like a champ after that job, with its fixed dimmer, new lighting kit, and replaced MK2a knob. Maybe something's worked loose?