PDP-8/S Computer

Here are some pictures of the PDP-8/S:

The PDP-8/S, front view.

The PDP-8/S, back view.

The PDP-8/S, left side.

The PDP-8/S, right side.

Like much of the stuff described on this site, this isn't working.

When I got it, one of the flip-chips had been removed, and was suspected of not working:

Bad flip-chip.

Indeed, inspection revealed a problem:

A bad solder joint.

Better solder joint.

After fixing that, I did some checkout of the power supply, reforming the capacitors and determining that it was safe to power the machine.

With the machine powered up, it didn't take long to discover that the bad card wasn't the only problem. Pressing LA and such doesn't accurately copy the contents of the switch register to MA.

The 8/S is a serial machine, so it actually takes many clocks of the shift registers even for such a simple operation. My next step will be to check the power supply for ripple, then check the internal clocking to see why it isn't reliable.

It came with a PT08 terminal controller and various extra flip-chips, shown here piled on and around the machine:

The PT08, side view.

The PT08, rear view.

The PT08 is necessary because it was not possible at the time to get both the terminal controller and the CPU to fit into the nice desktop box. Each PT08 controls a single serial terminal, usually an ASR33 with reader-run control and interfaced with current loops.

Last updated on 02/25/23 02:21