The problem with the unit, is the 400k drive rejects the disk, sometimes with a happy mac, sometimes without happy mac, rejecting disk, sometimes with an 0FXXXX sadmac code, sometimes it would boot all the way in, but that was very rare. I tried cleaning head and turning that adjustment screw, and redid the lithium grease where the mechanism is that handles the eject as it was malfunctining. nothin, i think the R/W alignment is out or the head is bad.

So i decided to stick a G3 style superdrive in there, my old and now destroyed 575 had the same drive, and i seen smoke from analog board, and then chirp-chirp-chirp from the analog board. I cannot find any charred remains of anything. yet....

Unplugged superdrive, machine fires up but still fails boot on the 400k drive, well tries to like before. The super drive causes power supply to whoop-whoop-whoop, so maybe shorted superdrive? it was one i had randomly laying around where i stripped a G3 beige years ago with an unstable logic board.