HP 2100A Restoration

Hayden Kroepfl perlpowers at gmail.com
Mon Aug 1 20:29:05 CDT 2016


I recently acquired a pair of HP 2100A minicomputers locally for very
cheap. Don't think I could get much more local that a guy literally at the
end of my street. He bought them at an auction over ten years ago, never
powered them on, and left them in his garage since. They've likely never
been powered up since they were last in regular use. The units seem to be
complete, apart from missing a few I/O cards that are written onto the top
of the power supply. I don't plan to power them up until I've taken them
apart, cleaned all the dirt and debris from them, and inspected the power

With regards to the power supply, I'm thinking my best bet would be to do a
power on with no cards in the system. Though I'm not sure if all the power
rails would even come up without a load on it, since it sounds like it may
do some power sequencing from what I've read. I was wondering if anyone has
some experience with testing a similar power supply that hasn't been run in
at least 10 years?

I'm not sure if using a variac to slowly warm up the supply and the caps
would be wise on one of these power supplies. I'm not sure how the
switching supplies would handle the low voltage at the start.

The only I/O card that was installed in both machines, besides a terminator
board in only one of them, is a serial interface made by some company with
the logo CMC. It uses a COM2502 UART which I was surprised to find a
datasheet for, however I haven't found any information on the card itself.
I have a photo of the card in the album linked below if anyone has any
information on it.

I know this email is getting a bit long, but with regards to the memory
both machines have a ID(16K) driver board, and two core modules. However
one machine has both core modules marked 02100-60052 on the bridge, and the
other has one marked 02100-60052 and the other 02100-60054. Is there any
difference between these modules? I'd assume by the 16K driver in both,
that all of the core modules are 8KW modules. Would that just be a later
revision or is one a different size?

I've taken some photos of the machines and put them here:

I'll be taking more after I make some space to start taking the units apart
for cleaning and inspection. I've also included photos of the serial
numbers and other badges on the backs if anyone knows of a resource to
decode them.

I'd very much appreciate any help or suggestions that people have. I really
want to get at least one of these machines back into full working order to
have some fun programming with.


Hayden K.

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