ICL PERQ 2 T2 Micropolis 1303 spinning down.

Mattis Lind mattislind at gmail.com
Sat Jan 2 08:20:51 CST 2021

Worked a bit more with this drive.

Removed the PCB and found the combined brake and head lock solenoid. It
operated freely. As I couldn't find any way of observing the head
positioning mechanism from the outside I opened the lid of the drive. With
the solenoid in the unlocked position it was possible to move the heads so
they were not stuck at least.

Reassembled the drive and now it spun up and it sounded like it was moving
the head back and forth. It continued to do so for a minute and then spun
down. I managed to repeat this two times and then it reverted to the old
behaviour of not spinning up at all.

I am not sure what this indicates. Perhaps it fails to servo information?
It doesn't look like a mechanical problem but I am not sure. Unfortunately
I don't have any other Micropolis 1303 drive around so I cannot replace any
electronics to see if it works any better. It seems to be quite different
from the Micropolis drives that where schematic are available on bitsavers
so fault tracing the circuitry will be hard.

I will probably need to consider this drive as toast even though it would
have been really interesting to know more of what PERQ system there was on
it, unless someone comes up with some bright idea on how to recover the


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