8 Jul
2003
8 Jul
'03
10:03 a.m.
--- Jim Davis <jpdavis(a)gorge.net> wrote:
Ethan Dicks wrote:
Dunno. I can say categorically that they were failed chips. They
did not pass muster in a handheld TTL tester, and when replaced,
the PDP-8/L worked.
There was a mention on the list of a batch of 7440s that failed in
another M-series machine (might or might not have been an -8/L)
with the same date code.
Not sure why 7474s from the mid-to-late 1960s would be more fragile
than, say, 7400s. Perhaps the flipping and the flopping wears them
out faster than anding and oring? :-)
-ethan
That's been my experience, too. I have
replaced as many as 8 7474s
at a go to get an -8/L back on its feet. I don't recall replacing
any other chip, as a matter of fact.
-ethan
7474's Dead d flops? whats the story on that?
Jim