Building a new VT100 power supply


Building a new VT100 power supply by Brian Benchoff.

A while back I found one of these – a VT100 serial terminal from 1979 – on eBay for cheap. $40 and a whole lot of waiting later, I had it on my desk. I turned it on, and… nothing.

I expected this. The auction said it didn’t work. After tearing it apart and seeing what *could* be wrong, I found the switching transistor (yes, this thing actually used a switching power supply in 1979. It’s a really well engineered piece of equipment) was dead. If anyone knows where I can get an IR 92-O350 transistor – it looks exactly like this– drop me a line.

Instead of rebuilding the power supply with incredibly difficult to find parts, I found this tutorial for improvising a VT100 power supply with a normal, off the shelf ATX computer power supply. The circuit is fairly simple, although the non-volatile RAM in the VT100 requires -23 Volts. No big deal, just make a crappy linear supply for that.

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