14 Jan
2003
14 Jan
'03
1:57 p.m.
--- Charles <charlesmorris(a)direcway.com> wrote:
I'm still looking for an M220 board since one of
the six won't
carry from its LSB to MSB. Probably just needs a 7482 adder; I
have one on order.
All I have (not installed in working machines) is short stack of
defective M220 modules. If you have an extender card, you should
be able to trace the fault pretty quickly with a logic probe or
an oscilloscope.
Without an extender card, it's a lot harder.
This weekend, after quite a bit of signal chasing, I
found that I
had put the variable delay line in the wrong slot some time ago
while cleaning connectors/mice nests!
I've done stuff like that.
When I replaced it in the
correct slot there was still no STROBE output. I then found that
the 7400 output buffer was internally shorted to Vcc (probably
from the mis-slotting). Replaced the 7400. Now it cycles.
I wouldn't be so sure that it was hosed by that. M-series modules
use the 4 pins for power and 32 pins for signals. It's possible
that you accidentally hooked two outputs together and the 7400
lost, but it's also possible that it was previously hosed.
-ethan
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