23 Jan
2012
23 Jan
'12
5:39 p.m.
Tony Duell wrote:
The advantage of the signature analyzer (SA) was you can deal with
circuits that have feedback loops more easilyand without the need to
fully understand the operation of the circuit. For example servicing
Atari Asteroid/Tempest/Battlezone vector generator (XY video games)
there is a signature for each pin and thus you start at one end and work
to the other of the schematic, where the signatures don't match you then
have a likely suspect -slap on the logic comparator (Bugtrap or HP) or
replace the chip. This often found the problem within a few minutes of
setting up the tests.
The primary saving was more lower level technicians could fix board that
would previously have required far more training - and in a small
service shop (or distributor repair facility) where you may only see
that board once or twice a year it wasn't worth the time to learn all
the workings to be able to fix it quickly.
I use SA from time to time - it doesn't always help, but it is just one
more tool on the shelf to get stuff fixed quickly...
John :-#)#
--
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
www.flippers.com
"Old pinballers never die, they just flip out"
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