Getting Started

A physical inspection of the machine is always the best place to start a restoration project.  This PDP-8 had been stored reasonably well over the years, and there was little visible signs of rust on the chassis, however many transistor legs had rusted and many of the transistors had fallen off their PCB’s. The glass front panel was broken in two pieces and was unusable.  However, the backplane wiring appeared to be in good shape, no bent pins or signs of damage.

The Maintenance Manual helpfully provides a board layout by slot so it’s possible to confirm that a full set of boards necessary for the machine to operate are installed, and most importantly, they are in the correct slots. It’s worth noting that the slots are numbered from Left to Right while looking internally at the backplane.  However when you are looking at the card side of the chassis, the numbering is reversed.  There is no PCB backplane, all pins are wired point to point.

Also, the backplane pins are alphabetically numbered, missing letters likely to confuse, so you do need to learn a new shortened alphabet:


Note: The black core memory box at the top of the left chassis.

Left card cage followed by Right card cage: