2 Aug
2016
2 Aug
'16
3:54 p.m.
Well I'm hoping for the memory section that I can find at least one of the
4 core boards that works right away. I've got an 8k driver board I can swap
it so I could run the system on only a single core board if needed. I'd
probably write a short program to do a bunch of memory writes, reads, and
such to exercise it for a few hours or such.
The power supply going bang is one of my worries. I've got an old 80s logic
analyzer with power supply issues, while testing got a big spark by one of
the huge filter caps in it and it put me off working on it for a long while
XD.
It would have been quite nice if there was no CTuL logic in the system,
when repairing my Altair if I find a dead logic chip I can still buy modern
compatible replacements. If one of these die, I'd probably have to build a
circuit out of discrete transistors on an ugly protoboard.
On Tue, Aug 2, 2016 at 3:46 PM, Rik Bos <hp-fix at xs4all.nl> wrote:
-----Oorspronkelijk bericht-----
Van: cctalk [mailto:cctalk-bounces at classiccmp.org] Namens Jay West
Verzonden: dinsdag 2 augustus 2016 23:24
Aan: 'General Discussion: On-Topic and Off-Topic Posts'
Onderwerp: RE: HP 2100A Restoration
There is an HP book specifically on I/O interfacing to the 2100 (and
21MX) I/O
bus. I think there's also an abbreviated
chapter on it in a different
manual. I'll see
if I can dig up the name and if it's online
anywhere.
I've restored at least five 2100's, and run a dual cpu 2100A & 2100S
system
regularly. I have never heard of nor seen a power
supply failure on any
of them.
The power supply always came up with little or no
pot adjustment, and
nothing
else required. I'd be surprised if your PS
needed any attention unless
they were
under water.
Debugging the memory section is a far different matter. It's far *far*
easier
to
troubleshoot if you have a known working set. If
not, it's very easy for
boards to
test ok and then later fail and then later test
ok (bad upper section of
a 16K
driver, etc.).
J
About power supply failures mine did have one, when under power after a
few minutes there was a loud bang and the system resets.
Which would be repeated every few minutes, some investigating and
measurement later I discovered one of the high voltage elco's shorted every
few minutes.
Which started the power on cycle and resets the cpu.
After replacing those all voltages were stable and in range and the
banging was over ;)
After some testing I concluded there were some faults in the cpu, being
the lucky owner of an extender board I was able to fix all the errors.
The HP 2100 service manual and hardware course and engineering reference
are a big help fixing the 2100 and as J says a set of known good cards can
be of help too.
But knowledge of the working of the micro instructions is also a big help,
IRC the micro instructions are described in both the engineering reference
and the service manual both can be found on bitsavers.
The only weak point of the 2100 is the use of uCTL a Fiarchild DTL
derivate used for IO drivers in the 2100 series.
Brent Hilpert has a lot of info on his site about those gates.
-Rik