PDP-11/40 Restoration 2025

10/29/25

We did an initial assessment of the PDP-11/40 cabinet and chassis.

• There are old and new PDP-11/40 chassis. This is the older design.

• The first power distribution backplane has two burnt connector contacts for the +5V source

• The power connector that mates to the first power distribution backplane is missing the two +5V contacts and the housing is burnt where the contacts go

• The power feed wire harness for the first power distribution backplane was modified to feed +5V to the PDP-11/23 backplane. We need to restore this to the original configuration to power the PDP-11/40 CPU boards.

• There are only two +5V power supplies installed. If we install Unibus boards in the back of the chassis we will need to install a third +5V power supply.

• We have a PDP-11/40 expansion chassis in the warehouse that we can use to repair this chassis.

We replaced the modified filler panel below the front console with a normal filler panel.

We removed the non-DEC power supplies that were mounted to the rear swing frame.

We removed the PDP-11/23 boards and Q-Bus backplane.

We replaced the damaged KY11-D Programmer's Console with an undamaged one.

We removed the oscilloscope and lab power supply from the CPU chassis. The idea was to install the Tektronix RM504 oscilloscope in the PDP-9 as a future graphics display, but we really should use an RM503. We have several RM503 oscilloscopes in the warehouse to choose from. 

To Do:

Repair or replace the first power distribution backplane

Repair the first power supply to power distribution backplane connector and power harness

Test the power subsystem

Install the PDP-11/40 CPU backplane, CPU boards, Memory board, and Unibus terminator from this system

Test and repair the KY11-D Programmer's Console

Install a H754 +20, -5V power supply of we install core memory

Install the TU65-H in the cabinet with the TC11 DECtape controller

Connect the TC11 to the end of the Unibus in the 11/40 chassis