A420/1 Floppy Drive
I thought of using the step setting, which sets the disc drive timings and is more or less equivalent to the FDRIVE setting on the Master series, although I didn't understand the correlation between the given setting and the reported settings, so I tried them all out here.
None of that worked, anyhow, so I am a bit stuck, as there is no fault-finding guide in the service manual. It could be the 1772 controller or one of the associated logic chips, but I am not going to go changing them speculatively.
