16 Nov
2013
16 Nov
'13
10:03 p.m.
Hello all,
I have a PDP-11/44 I want to get the basic tests done before I go further as I
have work ahead of me.
Backstory: all the cables in the rear were cut. (No big deal, I can rig up a
TU58, console, power, and other cables easily). I got the mains cable
connected and my Kill-A-Watt shows 13W with the 11/44 "on". This is far as I
have managed to get.
I do occasionally hear a clicking from the PSU...it's sporadic, unpredictable,
current draw does not increase, no smoke, and no visible arcing. It confuses
me.
I then decided to try the "jumper pins 1 and 3 or 2 and 3 or 1 and 2" to see
what would happen. The result? Nothing! I then decided to measure the
voltages using pin 3 as the reference. 1 (power request) and 3: -0.01VDC, 2
(power inhibit/emergency shutdown) and 3: 2VDC, 1VAC. This strikes me
as...bizarre. Should I have AC there or is my multimeter/my my multimeter
skills at fault?
I proceeded to follow this logic: "Hmmm. Emergency Shutdown is 2V...that could
mean the emergency shutdown state is set. I notice there's an "airflow
sensor"
board in the PSU. Let's remove it in case it failed somehow." No change
there.
Any further ideas? The clicking confuses me...it's fairly quiet...something
I'd expect from something arcing internally and not a relay. The patterm in't
"click-click-click-click" like a relay toggling...it's more random and
sporadic
with no reproducable cause. It seems to come from the lefthand side (with the
power cord on the left).
Does anyone have the pinouts for the console cable? I'll need to make one of
those up. Same with a cable for a DEUNA.
--
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects
17 Nov
17 Nov
12:07 p.m.
Hello all,
I have a PDP-11/44 I want to get the basic tests done before I go further as I
have work ahead of me.
Backstory: all the cables in the rear were cut. (No big deal, I can rig up a
TU58, console, power, and other cables easily). I got the mains cable
connected and my Kill-A-Watt shows 13W with the 11/44 "on". This is far as I
have managed to get.
I do occasionally hear a clicking from the PSU...it's sporadic, unpredictable,
current draw does not increase, no smoke, and no visible arcing. It confuses
me.
I then decided to try the "jumper pins 1 and 3 or 2 and 3 or 1 and 2" to see
what would happen. The result? Nothing! I then decided to measure the
IIRC the power cotnrolelr conenctor in the 11/44 is jsut conencted to
switch contacts. It is used to turn on power cotnrollers when the machine
is turned out. You can't use it to turn on the 11/44 CPU itself. THat can
only be done with the keyswitch on the panel.
As you probably know, the keyswtich has no pins, any key that will fit
into the switch will turn it.
voltages using pin 3 as the reference. 1 (power
request) and 3: -0.01VDC, 2
(power inhibit/emergency shutdown) and 3: 2VDC, 1VAC. This strikes me
as...bizarre. Should I have AC there or is my multimeter/my my multimeter
skills at fault?
I suspect that's jsut random noise pickup
I proceeded to follow this logic: "Hmmm. Emergency Shutdown is 2V...that could
mean the emergency shutdown state is set. I notice there's an "airflow
sensor"
board in the PSU. Let's remove it in case it failed somehow." No change
there.
Is there? There's an overheat sensor switch, but I don't remember
anythign else.
The 11/44 PSU is normally an H7140. This is a very complex supply that I
would not want otwork on without the printset.
There are 2 main PSUs. One produces the +5V, +15V amnd-15V for the CPU
and I/O boards.
The other starts of producing 36V. This can be battery-backed (IIRC 18
Cyclon cells and a fiar amount of electornics). The cooling fans run off
this supply via a chopper circuit (The fans are 35V, 70Hz AC ones). This
supply is also regualted down (swithcing regulators) to give the voltages
for the memory boards.
The control circuity has its own PSU. And it's another switcher. This
time a fairly conventioanl desing. While the 2 main SPUs have their
control circutrry isolated fro mthe maisn, this one doesn't. It';s mostly
live,
The leftmost board in the chassis -- the 'bias and interface' board --
contains the control circuitry for the control supply, the logic to
enable the other suppleis, and the fan driver circuit. The next 2 bords
are the memory supply. The right hand 2 boards are the lgoic supply. I
think th battery backup unit involves another PCB next ot the
bias/interface one.
All 3 of the SMPUS run off the same 350V or so DC rail, obtaiend by
rectifying and smoothign the mains -- the 2 large capacitors at the far
left. This 350V is distributes othte memroy nd logic supplies by the
2-way barrier strips on the top of said board.s. Be _very_ careful. If
you touch that, most likely you will not feel it. Ever.
Any further ideas? The clicking confuses
me...it's fairly quiet...something
I'd expect from something arcing internally and not a relay. The patterm in't
When mains i appleid, the control supply shouold be running. Is it
possible it's tripping for somne reason? That could produce a soft click
from the transformer.
There is a relay, under the chasis. It is part of the sinrush limiter
circuit. It is supposed to short out a couple of resistors once the
supply has got going.
"click-click-click-click" like a relay
toggling...it's more random and sporadic
with no reproducable cause. It seems to come from the lefthand side (with the
power cord on the left).
Alas boat hthe control supply and the inrush limtie relay are on the left.
Does anyone have the pinouts for the console cable? I'll need to make one of
those up. Same with a cable for a DEUNA.
There should be an 11/44 printset on bitsavers. That will give the
schematics of the PSU and the pinouts of the console and TU58 connectors.
-tony
4053
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4053
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