4 Mar
2008
4 Mar
'08
1:16 p.m.
Not so useful with peripherals though, I find a
storage scope is
invaluable for them, the more traces the better, so I suppose a logic
analyser would be useful, but does one exists for MINUS 6.3 volt
logic? I always presumed they were only invented after silicon
replaced germanium and so only work with positive logic voltages.
I fail to see what silicon .vs. germanium has to d owith the polarity of
the logic cignals. In general PNP transistors, and for that matter PMOS
fets, imply -ve logic levels, and plenty of machines were built using
those components. Also ECL chips have -ve logic levels (around -2V) wrt
ground.
The HP Logicdart (a handheld 3-input logic analyser) can certainly handle
the PMOS logic signals in older HP handheld calculaotrs and the -15V
logic levels in the discrete transistor circuitry of the HP9100. I don't
see why it'd not work for you. And most _decent_ logic analysers (as
opposed to the TTL-only toys...) can handle ECL levels.
In cany case, I cna't believe the signals in your machine are all that
fast. Is it not possible to make up level shifter stages to turn them
into TTL-level sgiansl for testing?
-tony