23 Jan
2012
23 Jan
'12
1:32 p.m.
On 22/01/12 00:41, Dave McGuire wrote:
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.
Hey folks. I have a short-term need for an HP signature analyzer. I
don't need one of these very often, so I'm not really keen on buying
one. (I know...those here who have seen my lab may be astonished to
learn that there's a piece of test equipment that I do not have...but
this particular one is rather boring, and not one of HP's better ideas)
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.
There's literally nothing to it except a CRC generator mated to a hex
The CRC polynomial is farily obviously critical. Did all signature
analyser manufacturewrs use the same one?
display with a custom character table (if memory
serves: 0-9ACFHPU
instead of 0-9A-F) to dissuade attempts to figure out "this code means
this error" troubleshooting. I think the best way to think of it is as a
Hmm.. I am pretty sdure the display table was given in the manual, so you
could work out the bit-level contents of the shift register. How easy it
is gto go from that to the actual signal patttern is another matter...
digital version of an analog signal tracer...
(although perhaps a pulser
and a logic probe would be a better analogue for that?)
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.
-tony