HP 2100A Restoration

[Bob Rosenbloom]

On 8/1/2016 6:29 PM, Hayden Kroepfl wrote:
> Hi,
>
>
> 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
> supply.
>
> 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:
> https://goo.gl/photos/z2tGBbNvekwrxS5L9
>
> 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.
>
>
> Thanks,
>
> Hayden K.
>

It's a low frequency, 800Hz IIRC, switcher so don't use a Variac and do 
have a load.

There's a separate manual for the power supply: 
02100-60053_PowerSupplyFor2100And2155A_OperatingAndServiceManual_5951-3038_199pages_Apr74.pdf
(from bitsavers). It has everything you need.

There's a bunch of small electrolytic capacitors on the Inhibit Driver 
Load Card, A106, that needed to be reformed before my memory would work 
reliably.
They reformed themselves in one of my units. I had memory errors for an 
hour or so then they went away. On other units, I reformed the caps 
(took the board
out and slowly brought it up on a bench supply), and had no memory 
errors at first power up of the system.

Bob

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