15 Oct
2005
15 Oct
'05
8:04 p.m.
I've been looking for schematics for this machine
since the early 1990's,
and
as yet have come up dry. They just don't seem to be out there. My
understanding
is that generally, service technicians in the field were trained to repair
the machines
on a module basis, e.g., replace this circuit board if it exhibits this
symptom.
HP had much the same policy. AFAIK there is no HP desktop calculator
service manual that contains schematics of the logic stuff. If you're
lucky you get the PSU scheamtics. This includes the 9100, 98x0, 98x5 and
even the 46/81 machines. For some odd reason, the HP80-series computer
service manuals did include schematics, but the HP9000 ones didn't. Oh
well...
The HP serivce manuals (the ones I've seen) are mostly useless _BUT_ I
still recomend reading them. The reason is occasionally you get some
information 'in passing' which is very useful if read with a hackish eye
Service technicians didn't need schematics,
because all they really needed
was
troubleshooting guide, a knowledge of general operating theory, good test
equipment,
and a kit full of every spare assembly needed. This made it unnecessary for
I am not going to post my rant about board-swapping again. Suffice it to
say that's not how I reparied any of my HPs. And it's not how I'd repair
a Friden if I was lucky enough to have one.
them to repair things down to the component level,
except in the case of the
power
supply, which may require replacement of individual components. Everything
else was modular. As a result, field techs likely didn't need schematics --
and
that was a good thing, because field techs could be 'loose' in their care
of schematics, allowing copies to be made, leaving them behind, etc., which
will
generally not maliciously intended, could result in competitors getting
their hands
on the design, which, in those days as it is today, can be a big problem.
Hmmm..... Having done battle -- and won -- with producing repair
schematics for the HPs, I am not sure this is valid. Certainly for the HP
machines there's a lot more needed than just a schematic for copying the
machine (ROM contents, and there were custom chips in some of the later
machines, for example). And it's not _that_ hard to produce a schematic
given time. The lack of official schemaitcs might slow down copying
efforts, but it wouldn't make much difference in the end (it's either
going to be easily possible with or without the official schematics, or
very difficult with or without the schematics, depending on the prsense
of custom parts).
To copy the machine, a simple netlist would be essentially all you need,
along with a rough PCB layout (assuming you're not just going to copy the
PCB foils as well). That would be next-to-useless for repair, you need an
annotated, logically set out schematic.
-tony