Hey Tony (Duell), [or anyone else interested for that matter]
want to help me with my 11/45 again? I just found out that I
again have too much time on my hands, so I'm ready to try some more. I've
moved to a new house and brought my entire pdp11 collection with me (most
of it is in the garage). I placed the '45 (w/ two TU10s, a stack of
RK05s, a rack of SMD disks, and a tek4015) in the 'great room' here and
there's plenty of room to tinker. BTW, it looks really cool with my red
walls. I think I'm going to keep it here permanently.
Here's a little refresher as to what we were on last time:
PS. Is this a grant thing perhaps? What if somebody took a DMA device
out of one of the slots without replacing the jumper? Would it do this?
On Sat, 19 Jun 1999, Tony Duell wrote:
Hey All, sorry I took so long to get back to this topic, but things have
been hectic and there's been no time for Geek Stuff. :( :( :(
I removed the extraneous things from the bus (namely the external box of
memory and the three core SUs), so now I have only the 11/45 backplane
with an M930 in the last slot. Still the same symptoms on the front
OK, it _is_ an M930 terminator and not an M9302, then. I was going to ask
you about that. The reason is that the later M9302 board can 'lock the
unibus' if there are grant problems. An M930 won't.
The probe of J14 revealed the following:
on 2&3: exactly 15VDC (this is the 15v source you ask about being
present and correct, isn't it?)
Sounds perfect to me. And yet _both_ H745s are giving no output?
There should be an H745 in the rear slot of the top PSU. It has an 8 pin
connector on top. Pin 1 is the -15V output. Pins 4 and 5 are a +15V
on 8 : about 4VDC
on 10 : Zero.
Puzzling, but not necessarily a problem yet...
on 12 : about 4VDC
Sounds right again.
To answer a few of your other questions:
I don't have a KM11 maintenance board.
Pity. I didn't think you'd have one, but it was worth asking.
I have the 8-pin, flat power connectors on my
I think _all_ 11/45 systems have the 8 pin connectors on the CPU
backplane. The difference is how the extra System Unit backplanes get power
On old machined (pre S/N 2000?) there was a PCB on the inside back of the
CPU box. It had a number of 8-pin flat connectors on it. The system units
plugged into that.
On later machines there was a board on top of the CPU fram on the RHS
(over the 'hole' that goes over the PSUs). System units had the
conventional 15 pin and 6 pin connectors.
Which schematics are you using?
I have the DEC field maintenance printset for the 11/45 (both versions).
What should I do next?
You mentioned that 'both -15V outputs are low' Which pins of which
connectors are you measuring? At the PSU there are 3 -15V lines on my
diagrams - pin one of P21 (top PSU rear slot H745), pin one of P25
(bottom PSU, front slot, H745) and pin 4 of P22 (bottom PSU, 12 pin
connector on transformer housing). Which (any/all?) of those are missing?