7 Sep
2014
7 Sep
'14
11:31 p.m.
2014-09-07 22:38 GMT+02:00 Brent Hilpert <hilpert at cs.ubc.ca>:
I remember that solitary N8885A when reverse-engineering the 9830, and
checking for a 7400 equivalent.
The 7436 seems to be pretty much non-existent. There's an obscure
reference here:
http://www.datasheetarchive.com/dl/Scans-005/Scans-00104143.pdf
The strange thing is there are half-a-dozen 7402s in the machine.
Looking at the specs they may have used the 8885 because it's slightly
faster than the 7402 and it doesn't look like a 74H02 was being made, but
to a cursory examination I don't see where the few nS benefit would be
needed in the circuit.
Oh well .. if you use a 74LS02 or 74S02 at least it's only two pins that
have to be swapped.
Yes. I could install a 7402 type chip 180 degrees rotated and just swap
the power
pins, I guess. But I happened to find used N8885 pulls at $0.50
each, so I bought a few. Hope that they are better.
I checked the rest of the boards in the machine. Other than already faulty
ones I found that there are no more than maybe five or six NS chips in it.
Two of them seems to be working and three or four are just standard 74xx
chips. There is one more N8885 chip in the memory section.