11 Nov
2005
11 Nov
'05
4:26 p.m.
David Comley wrote:
I have been trying on and off for a while to map out
the schematic for the PSU of an HP7908 disc/tape unit.
There's a transistor I can't identify on the board and
I am wondering whether anyone can ID this thing for
me. The markings show "239" and then the batwings, and
then below that it says "4-456". Same problem for a
number of the diodes that are labeled "GE010673".
Partial help:
"4-456" is probably a short version of the HP house number,
the more complete number is likely "1854-0456".
If there's no manual for the 7908 on bitsavers, a (tedious)
route is find an HP manual for similar equipment (from the
same period and which has a chance of using the same part)
and scan the parts lists for the partial number.
Real-world example: While working on the power supply for an HP 2116,
I came across a transistor stamped "3-063". The schematic and parts
lists in the HP manual showed it to correlate to HP house number
"1853-0063". The parts list then cross-ref'd this to Motorola MJ2268.
If I recall, on the occasions when I've run across this in HP equipment
from the late-60s/early-70s, the unstated prefix has
been "185x".
I don't know for sure whether it could be another prefix
or not.