>Eric Smith wrote:
>DEC MK11-B Field Maintenance Print Set, October 1977
Thanks, Eric! I was just about to post that I discovered it's also in the
PDP-11/04 maintenance print on Bitsavers, although it's not in the 11/34 print
- go figure...
I didn't actually need the schematic, although I certainly used it this time.
The H7441 has a giant inductor (L1 in the schematic) that's physically bolted
to the PCB. It a U-channel thing that looks like a transformer but is actually
just a big 30+ amp choke. Some PCB layout guy decided it was a good idea to
run the +5V output and ground traces directly under this choke so, unless it's
elevated above the PCB, it will short the output! I think it must have
originally had some kind of rubber or fiber washers underneath it, but in mine
the washers had disintegrated and were nowhere to be found. I could tell that
it was shorted somewhere, but I kept thinking that it must be a bad capacitor
or a shorted crowbar, and I'm embarrassed to say that it took me more than an
hour to figure out that it was the frame on the choke. I carved up a rubber
grommet with an X-acto to make some spacers and now it's as good as new.
Bob
