jpdavis sez...
>
> Robert Krten wrote:
>
> > <snip>
> >
> >:-)
> >
> >In my case, the failure modes were as follows:
> >
> >2 chips failed with: grounding the PRESET line caused the Q
> >to go high as expected, but when PRESET was left floating Q
> >went low. [DEC leaves the PRESET and CLEAR lines floating on
> >various modules, so I consider this a fair test].
> >
> >1 chip failed with insufficient +5 on the Q (or bar-Q, forget
> >right at this instant) output. The measured output was something
> >like 1.6V.
> >
> ><snip>
> >
> >
> That sounds like a design flaw. Even with TTL, unused inputs should be
> tied to somthing.
> What was the fanout for the Q /Q on the fried output?
This was not in-circuit, this was in a test jig. I don't know what the
in-circuit fanout would have been, that would require massive amounts
of digging through the schematics :-)
Cheers,
-RK
--
Robert Krten, PARSE Software Devices +1 613 599 8316.
Realtime Systems Architecture, Consulting and Training at www.parse.com
Looking for Digital Equipment Corp. PDP-1 through PDP-15 minicomputers!
Received on Mon Jul 21 2003 - 13:11:36 BST