PDP-12 Restoration at the RICM

Jon Elson elson at pico-systems.com
Sun Jun 5 20:54:22 CDT 2016

On 06/05/2016 09:54 AM, Michael Thompson wrote:
> 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.
2525 and 5252 sound VERY much like test patterns.


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