AR 8/600: Build log #5

I did not die. Here is another update to the relay computer:

Finished Control Unit, PSU and pretty much everything. In this post I will show only the CU and PSU, and when I get the time I will make more videos and take some photos of the whole machine.

DSCI1863The beginning.

DSCI1865Instruction register is ready, starting opcode decoder.

DSCI1868Some of the sequencer is also ready.

DSCI1869Things start getting serious.

DSCI1873More option decoder wiring.

DSCI1875Wires n’ Relays.

DSCI1890Some days later, the CU is almost finished.

DSCI1891I forgot to take a photo of the finished CU before mounting it into the cabinet, so have this one instead.

Power Supply Unit

DSCI1985LM317 adjustable voltage regulator provides the voltage reference…

DSCI1986…which is sent to two 2N3055 transistors…

DSCI1987…which sends the power to the control panel, that delivers it to the whole computer.

DSCI1988The power supply is 90% made of reused components, including the transformer.


After I finished the inter-module wiring, I had a lot of debugging to do. The PC and some instructions were not working properly, due to timing errors, some unconnected wires, and problems with the power rails. After several days of debugging and lots of crocodile clips, the machine was working properly. Here is a video of the debugging phase:

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One Response to “AR 8/600: Build log #5”

  1. Awesome! There’s a home-built computer web-ring that you might be interested in. It’s at:

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