4 Sep
2011
4 Sep
'11
1:30 p.m.
On 09/04/2011 03:22 PM, Tony Duell wrote:
That is a DEC unique Open collector bus driver with high current outputs
and the input side has a Schmidt trigger input. The usual source is junk
boards. Its one of about 10 chips DEC develped and used for bus
interfacing
for Omnibus, Unibus and Qbus and was ideally suited for cable drivers
and peripheral IO.
Allison
Oops,
didn't check that properly! I really should have checked the full
function of the chip.
Pin 1 of the 158 is connected to a signal that is definitely wrong in that
it is Low when it should be High. Tracking this back it is looking like a
failure in a DEC 8837 chip which is listed as a "RECEIVER, BUS, HEX, UN".
Often DEC-numbered parts are selected versions of standard ICs with the
same number, bnd the parameter they're sleected for may not really matter
(!). Have you tried puting '8837' in one of the data sheet search engines
to see what comes up. If the function and pinout looks sane, it may be a
suitable device.
Hw many pins does htis device have? What is the full functionality (or
can you point me to an on-line copy of the printset so I can look over
the schematic)?
In particualr, does this cjip have enable inputs, and are they used (that
is, not tied to +5V/gnd as appropriate)? Yes, you really do have to check
everything.
-tony