Consolidated Computer Inc. PDP-8 Clone – Part 5 3rd PSU refurbishment.

So we are two power supplies down, one to go. This one is a bit of a monster with three main voltages and two extras.

Top down view of PSU 3 before cleaning.
Top down view of PSU 3 before cleaning.

As with the previous PSUs, this one transforms the mains into lower voltages, rectifies them into DC and smooths them out but like the others it does not regulate the voltages. That’s done by a number of regulator boards at the end of the main card cage.

As with the other PSUs, this one is also filthy and with questionable capacitors.

PSU 3 chassis split into three pieces before being cleaned.
PSU 3 chassis split into three pieces before being cleaned.

My first job was to split the two halves and see what we are dealing with. As you can see it’s a mucky mess with dirt everywhere and a lot of rust on the capacitor clips.

The capacitors were removed and tested and just like the other supplies, they were fine. They don’t make them like that any more.

The rear of PSU 3. There are 3 PCBs with fuses.
The rear of PSU 3 showing the PCBs and fuses.

The three PCBs were removed and cleaned up. I took a wire brush to the fuse holders and blade connectors, cleaned the fuses and gave the boards a general spruce up.

One or two of the spade connectors had perished and failed when I was removing them so I made some new cables with new spades and replaced some of the other, dodgy connectors.

I replaces a lot of the nuts and washers as they had corroded quite badly. I didn’t replace the capacitor clips as I want to keep as many original bits as possible but I gave them a good sanding to get the rust off before re-assembling the whole thing.

It all went back together and is looking good. The voltages seem OK too!.

Top down photo of PSU 3 after refurbishment.
Here is the finished unit. You can see the capacitors have been cleaned and refitted. As have the capacitor clips and the cables.

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