23 Jan
2012
23 Jan
'12
3:36 p.m.
On 01/23/2012 04:32 PM, Tony Duell wrote:
Well, I've found one I can borrow locally, and I've been offered one
for $75 to own. My main goal here is to get the instrument repaired for
my friend, not have the exercise of building a signature analyzer that I
can just go get for $75, given that it's a relatively uninteresting
piece of equipment. The 3456a is MUCH more interesting. :)
You could DIY
one from a couple of shift registers, an LS86 XOR gate, a
PROM or two and an LED display... There's an article covering the
technical minutiae in the HP Journal archives.
I seem to remember the service manual for one of the HP analysers on a
web site -- I think it was one of the arcade game sites. Agilent may have
a manual on their site too (they have a lot of old HP instrument manuals
for download).
The manual I saw incldued scheamtics. THere were a couple of PROMs (one
was just the 7-segment decoder), but it was fairly obvious how it worked. I never really saw the point of signature analysis. If
you got the right
signature then that signal was problaby correct, but if you got the wrong
signature, OK, the signal was not doing the right things, but it doesn't
really tell you _how_ it's malfunctioning. It strikes me as being a
little better than boardswapping, but only a little.
That saiid, if I could find an HP signature analyser at a low price I'd
probably add one to the collection, but I doubt i'd use it much.
Don't try to repair a 3456a, then. ;) Take a look at the service
manual. There are schematics, but no firmware listings for the MC6800
and (I think) 8048 that controls everything, and no info on the custom
ICs, and on top of that, it's a damn complex instrument to wander around
in. I need to find that list of HP internal chip numbers.
If HP had included better information in the service manual, this
wouldn't be an issue. And, oddly enough, this instrument dates from
squarely within the time when HP was publishing *excellent* service manuals.
-Dave
--
Dave McGuire
New Kensington, PA