DEC PDP-8/a Restoration Log

4/30/20

I brought the 3x CPU boards, 2x core memory boards, and the programmer's console home so I could use one of my personal PDP-8/a systems to test and debug these parts

I have found 3x defective ICs so far, and should have replacements next week

  • Front board, E10 SN7408, pin 8 has a weak pulldown
  • Register board, E15 SN74174 latch doesn't latch
  • Register board, E26 SN7475, latch does not latch

The 2x 40-pin ribbon cables that connects the programmer's console to the M8316 board had wire-wrap wires added.

It looks like they were trying to fix bad cables.

I also found that the programmer's console cables in my personal 8/a were bad

Click on the image for a larger view

5/10/20

I am documenting the switch settings on the boards

The CPU board is set to not autostart

The BOOT switch on the Limited Function Console will start the CPU

The CPU booted OS/8 from an RX01 diskette in my personal 8/a system

5/13/20

With the CPU, Option-I, and Option-II in my personal 8/a system it booted OS/8 from an RX01 diskette

A known good Programmer's Panel works OK with the Option-1 board.

The BOOT switch on the Limited Function Panel and the BOOT button on the Programmer's Panel will boot OS/8 from an RX01 diskette, so the boot ROMs are OK