HP 2100A Restoration

tony duell ard at p850ug1.demon.co.uk
Tue Aug 2 00:12:18 CDT 2016

You need to get all the service and diagrams manuals for this machine.
I think they are on bitsavers and the Australian HP museum site. You 
probably should go through both of said sites.

> 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.

It's an early-ish, somewhat unconventional, and rather complicated switch
mode PSU. It has its own service manual (the CPU manual does not cover
it), which is available from at least one of the sites I mentioned. IIRC the 
manual gives an initial startup/test procedure. You do run it up on a 
variac, I think, but not in the obvious way. There are separate mains
inputs for the PSU control circuitry (which has its own internal linear
PSU) and the choppers. You get the first one going, and then run up
the choppers. IIRC you do use a dummy load (that is mentioned in
the manual) and one part of the test even involves shorting out some 
of the outputs.

> 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?

That is the part number for the top connector board, not the core memory
itself. Electrically the 2 top connectors are identical (pin-pin wired I think). But
due to the fact that the top edge fingers on the core board are not aligned
with the bottom edge fingers (the core plane is a separate unit, you will 
see what I mean if you pull the boards), the spacing of the edge connectors
on the 2 types of top connector is different. The manual shows which to use


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