HP 2100A Restoration

Pete Lancashire pete at petelancashire.com
Mon Aug 1 22:11:59 CDT 2016

With the supplies being switchers do not use a autotransfomer (Variac). If
they were mine I would replace the caps even if it meant speing $100 or so
and waiting. And being switchers they will need a minimum load to operate


On Mon, Aug 1, 2016 at 7:12 PM, Lyle Bickley <lbickley at bickleywest.com>

> Hi Hayden,
> On Mon, 1 Aug 2016 19:29:05 -0600
> Hayden Kroepfl <perlpowers at gmail.com> wrote:
> --snip--
> > 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?
> Those of us who have brought up HP2100s that have been stored (even in
> military packaging) know the power supplies can be a "bear". The PS is
> a "fold out" deal - and never used to be repaired in the field by FEs.
> They were swapped with new units - and the failing supply sent back to
> HP for refurbishing. The process was detailed to me by a person who sold
> 2100's as an OEM for many years.
> That being said, they are a early design switching supply - and should
> have a load when powering them on.
> > 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.
> I would definitely NOT use a variac on them. It's best to check the
> caps (and reform if necessary) and then power it up with a load. You may
> have to "gently" (as in slowly) turn the PS on and off a number of times
> to work out the years of "dormancy" (reforming the capacitors that you
> can't get to ;)
> > 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.
> The 2100 has a weird I/O addressing scheme - so check the manual
> carefully. Moving a card from one location to another in the mainframe
> changes its address! That's very different from DEC (and many
> others) who had switches or jumpers on boards to change addresses.
> interrupts, etc.
> > 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?
> Look on bitsavers: http://bitsavers.trailing-edge.com/pdf/hp/21xx/
> and start reading manuals (particularly the Maintenance and Drawings).
> There a wealth of information to be found there - and it's what I used
> to get my 2100S running.
> --snip--
> > I'd very much appreciate any help or suggestions that peopleh ave. I
> > really want to get at least one of these machines back into full
> > working order to have some fun programming with.
> HP2100 restoration is very doable.
> And the 2100 has one of the best front panels going :)
> Like how can you not like buttons that light up when you push them!?
> Most of my problems with my 2100S were related to the power supply -
> and a few related to memory.
> Wishing you the best!!!
> Cheers,
> Lyle
> --
> 73      AF6WS
> Bickley Consulting West Inc.
> http://bickleywest.com
> "Black holes are where God is dividing by zero"

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