PDP-12 Restoration at the RICM

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