15 Oct
2007
15 Oct
'07
3:07 p.m.
bunch of those in there. (Looking...) Yup, here in
the "299B Disk Driv=
e"=20
manual I spot some 75453 and 75454 in several locations in there.
They were quite commonly used to drive head load solenoids, head
postiioner stepper motors and the like.
The only 8-pin
TTL chips I (just) rememebr the 7456 ands 7457 (I think)
which were /50 and /60 counters (desigend to get 1Hz clocks from Europe=
an
or US power lines)
Those were LS56 and 57, or at least that's what's in my parts page, if =
there=20
were earlier non-LS versions of them I haven't found any data on them. I= And speaking of 50 and 60 Hz, I have this digital
clock here that I got=20
*real* cheap, because it has a problem. it gains a LOT of time every ho=
ur. =20
Something like 10 minutes, maybe? I'm convinced that it's jumpered (or=20
something) for 50 Hz line power. :-)
If it was, it would add 72 minutes instead of 60 ever hour, I think. So
it would gain 12 minutes per hour. Sounds just like your problem.
Most LSI digital clock chips could be jumpered for 50Hz or 60Hz input.
SOme earely ones seem to have been 60Hz only (I've not seen one that's
50Hz only, but that may be because most of the books I've read on this
originiated in the States).
-tony