PDP-12 Restoration at the RICM

Michael Thompson michael.99.thompson at gmail.com
Sun Jun 5 09:54:51 CDT 2016

We fixed the RK05 disk this week. We replaced E3 (LM301A) and E1 (SN7404)
on the G938 Servo Preamp module. The COUNT PULSE FWD H and the COUNT PULSE
REV H signals from the G938 module are both working now. The drive will now
seek correctly using the jumpers described in the Maintenance Manual or
using seek-only instructions from the RK8-F controller.

We tried the OS/8 and LAPS-DIAL bootstraps, but the processor just halted.
The first page of core that was read from the pack contained a repeating
sequence of 2525-5252. Either the pack was used as a data-only pack, or
diagnostics were run on the pack. During the week I will use SIMH to make a
PDP-12 bootable OS/8 RK05 image. Next week we will use dumprest to make an
image of the disk pack, and then write OS/8 to the pack.

Michael Thompson

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