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
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?)
on 8 : about 4VDC
on 10 : Zero.
on 12 : about 4VDC
To answer a few of your other questions:
I don't have a KM11 maintenance board.
I have the 8-pin, flat power connectors on my CPU.
Which schematics are you using?
What should I do next?
On Thu, 27 May 1999, Tony Duell wrote:
I recently acquired a nice, rust-free, mostly-original 11/45 from
You're in luck. The 11/45 was the first '11 that I obtained, and I have
the manuals for it (printset, maintenace manual, etc).
an old lisp hacker in Los Altos Hills, CA. He
told me that it had been
running the last time he'd powered it up, which was in 1984 IIRC, but
sadly, something has gone awry and it won't run now, though it seems to be
It can be got to run again. I am certain of that.
I am going to assume that you don't have the KM11 maintenance board,
useful though it would be.
has 12 KW of core as well, so I guess I could cut
the bus down a bit more
for the purpose of debugging.
You don't need _any_ memory to start with. As this is an 11/45, the core
can't be on the processor backplane (which has special slots for
MOS/bipolar boards only). So stick the M930 in the top of the rearmost
slot (slot 28 IIRC) of the CPU backplane for the moment. You'll not be
able to do a lot, but the CPU will at least talk to the frontpanel in
that mode if everything is working right.
Mode of failure is such:
I powered up the shortened system and the front panel lights lit
[excitement]. Then I tried to examine some memory locations via the
panel, but when I hit HALT, the RUN light stayed lit. I tried every
That is a classic indication on the 11/45. If one of ACLO or DCLO (I
forget which) is asserted, the CPU microcode goes into a tight loop and
won't listen to the panel.
This is either something on the bus pulling one of those lines, or a
fault in the PSU/wiring.
combination of switches I thought was
appropriate, but the RUN light
wouldn't go off. (Sounds like a simple bus error, really.) Upon
realizing that something was amiss, I decabled all the power connectors
from the logic and tested the voltages, which, surprisingly, were all
about 6%-9% above spec (and I'm not too sure that my VOM is accurate even
Yes, the old power modules will rise a bit off-load. That is nothing to
Which version power cableform do you have? Old machines have a
distribution PCB inside the CPU box with 8 pin mate-n-lock (flat)
connectors on it. Later machines have a distribution panel on the frame
at the top right of the CPU with 6 and 15 pin connectors on it.
I have manuals for both types, BTW.
though it's analog). I didn't readjust
the voltages, but reconnected the
power cables to the logic boards and retested the voltage levels. All
stayed about the same except for the -15VDC. It dropped to about 2V. Same
reading on both -15V regulators, by the way, and they seem to be connected
This you aare going to _love_...
There are 3 -15V sources in an 11/45 PSU. There's an H745 regulator in
both power supplies (and they do, indeed feed different parts of the
machine). There's also a -15V feed from the power control board in the
lower PSU (this board generates what is normally considered to be a +15V
rail. On the lower PSU, the +ve side goes to ground, and the -ve side to
the rest of the machine).
There is also a +15V supply from the top PSU power control board. This is
needed by the H745 regulators. Is this pressent and correct?
Looking at the schematic, it appears that if DCLO is asserted (low), then
Q3 on this board will turn on. This will turn on Q2 and shut down the
+15V regulator. Aha.... But only if DCLO is asserted by the PSU, not by
anything else in the machine.
Start on J4/P14 (12 pin mate-n-lock) on the top PSU. On the transformer
housing at the front of the PSU, not on the regualtor blocks.
Pins 2 and 3 are the +15V output (They're linked together inside the
PSU). Pin 12 is DCLO (this is pulled up by resistors on the bus
terminator, so you must have the rest of the machine connected). Pin 8
and 10 (NOT commoned inside the PSU) are the ACLO pins.
Let me know how you get on. As I said, I have all the schematics of this
machine (including the PSU), and I've repaired mine on the odd occasion...