I have a Masterview 850 with a floppy disk drive DSMD113 and controller DSMC112. When I try to load the 6 system floppy disks it stalls at disk 1, there are no fault leds or fault status indication on the CPU. The r(Read) led on the drive card lights up but it's like the first disk starts being read but never finishes. I have tried the disks, drive and controller in another system and they work fine. When I first started, there was a problem with one of the memory boards(MSB175), the fault led was up, so I changed it for a new spare and the fault went away. One clue I have is that the green led on the disk drive is lit as soon as the system is started, the drive seems to want to read a disk straight away, before the memory is reset and before the load button is pressed. I'm leaning towards a problem with one or both of the memory cards, but it's hard to find with no fault or status indication and I cant connect with a masteraid.
I suspect that the power supply is gone, and I would also replace the disk drive. I've seen Masterviews where the inrush current of the diskdrive motor gave the power supply the last push it needed to fail. A few years ago the power supplies could still be repaired but you have to be lucky for the time frame as they where repaired batch wise. Don't know if they still can be repaired.