Subject: PDP-11/34 PSU Yet Again

From: Jeffrey Sharp <[email-masked]>
Date: Mon Mar 3 23:06:00 2003

Well, I finally got around to testing the PSU on my 11/34. I measured at the
backplane connectors with no backplanes plugged in. Everything checks out
except for the -5V and +20V. Accordingly, the LED at the bottom of the H745
brick (regulator 1) does not light. However, some of the other voltages
coming from the H745 (according to the BA11-K FMPS) seem to be OK.

Does anything in the machine even need -5V or +20V? If not, can I leave the
bad brick in place? I have: KD11-EA, KY11-LB, DL11-W, MS11-JP, M7850 parity,
DZ11-A, RK11-D. I'll be adding a RX11 at some point. Someone enlighten me,
please. :-)

I'm pretty sure I have a spare brick.

Also: what are these signals on the 6-pin backplane mate-n-locks?
  - AC LO
  - DC LO

Something I learned: If you have a H785 brick in your 11/34 BA11-KA cabinet,
ignore what the 11/34 and KY11-LB manuals say about battery backup and the
rotary power switch. You can indeed have a battery backup with a BA11-K, and
the switch on the KY11-LB works as you think it should. You must connect the
ribbon cable from the H785 to the corresponding connector on the KY11-LB, or
the H785 won't work. You must NOT connect the one-wire connector from the
H785 to P4(?) of the AC input box, or else your machine won't turn off,
regardless of the rotary switch. Clear as mud?

-- 
Jeffrey Sharp

---

From: Patrick Finnegan <[email-masked]>
Date: Mon Mar 3 23:25:01 2003

> DZ11-A, RK11-D. I'll be adding a RX11 at some point. Someone enlighten me,

Something makes me think that the -5V might be needed for the Unibus, but
I'm probably wrong.

> Also: what are these signals on the 6-pin backplane mate-n-locks?

Oooh, I know this one.  They are set to a logical 'high' state when the AC
voltage coming in or any of the output DC voltages are low, respectively.

Pat
--
Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
http://www-rcd.cc.purdue.edu

---

From: [email-masked] (Tony Duell)
Date: Tue Mar 4 17:56:17 2003

> coming from the H745 (according to the BA11-K FMPS) seem to be OK.

I thought the H745 provided +20V and -5V only. What other voltage do you 
think it's providing...

> Does anything in the machine even need -5V or +20V? If not, can I leave the

AFAIK it's only needed if you have core memory. Certainly I've run 11/34 
machines without one, with MOS memory and a fair selection of interfaces. 
Generally you only need the +5V, +15V, -15V lines.

> bad brick in place? I have: KD11-EA, KY11-LB, DL11-W, MS11-JP, M7850 parity,

I would unplug the 8 pin connector from any brick you're not actually 
using, particularly if it seems to be defective. Since that's all the 
connections to the brick, the defective brick can be left physically in 
the chassis.

> Also: what are these signals on the 6-pin backplane mate-n-locks?

Power fail lines (like the Power Good line on a PC/AT PSU). Basically, 
any device/mounting box can pull those lines low if it detects a power 
failure, and the CPU (or other devices can then shut down in an orderly 
fashion.

-tony

---

From: Jeffrey Sharp <[email-masked]>
Date: Tue Mar 4 19:59:01 2003

On Tuesday, March 4, 2003, Tony Duell wrote:
>> Well, I finally got around to testing the PSU on my 11/34. ... Everything
>> checks out except for the -5V and +20V. ... However, some of the other
>> voltages coming from the H745 (according to the BA11-K FMPS) seem to be
>> OK.
>

My multimeter shows the following voltages on the mate-n-lock connectors
J3,5,7,9,11 relative to pin 8 (ground):

    +15V at pin  6
     +5V at pin 12
    -15V at pin 15

The printset -- specifically, sheet 2 of 5410864-0-1 "PWR DIST BOARD" (page
40 of the BA11-K FMPS PDF I downloaded) -- leads me to believe that these
voltages can come only from the H745.

Other documents agree with you, though. I'm confused.

> connections to the brick, the defective brick can be left physically in

Thanks. My next step, then, is to pull the cards, inspect them, and clean
out the backplanes and other currently hard-to-reach spots. Then I'll check
for bent pins on the backplanes and eventually test a minimal card set.

I'll double-check, but it looks like all my NPG jumpers are in. I don't have
any NPR peripherals except for the RK11-D, and I have ample "bleeding
knuckle" G727A grant cards. I don't *expect* any grant issues.

-- 
Jeffrey Sharp

---

From: [email-masked] (Tony Duell)
Date: Wed Mar 5 16:38:00 2003

> voltages can come only from the H745.

Are you sure? I've not got the prints in front of me, but I thought all 
the -15V lines came from the H754 module, and the +5Vs from 
H744/H7440/H7441 modules. With the +15V coming from the PCB under the 
mains transformer.

Oh, hang on.. I know what you're seeing, I think. Those are the Vb 
(battery-backed) lines. The battery backup interface brick fits in place 
of the H745 -- the idea being that you only need the H745 if you have core 
memory, which is non-volatile, and you only need the battery backup unit 
if you have (volatile) MOS memory. The battery interface uses a different 
8 pin mate-n-lock connector in the harness, though.

If you don't have the battery backup unit, then the Vb lines are linked 
to the normal rails via jumpers (on the backplane I believe).

-tony

---

From: Jeffrey Sharp <[email-masked]>
Date: Thu Mar 6 00:54:00 2003

Thanks for your help, Tony and Patrick. I think I have this mostly
understood. Just a few things remain.

> 8 pin mate-n-lock connector in the harness, though.

Ok, problem found: me. I got confused by the print set on the representation
of front vs back views, and thus I had my regulator positions backwards. We
were both also confusing the H745 and H754. Everything (except one thing)
looks fine now. Here's what I have:

   Under Xformer  +15V
   Brick 1: H745  -15V
   Brick 2: H7441 +5V
   Brick 3: H7441 +5V
   Brick 4: H785  +5VB, +15VB, -15VB

The H785 doesn't produce -5V or +20, so it is certainly OK that I'm not
finding those voltages on the backplane power connectors!

My current understanding (no pun intended) of the H785 is that when it is
not running off the battery, it produces +5VB, +15VB, and -15VB with current
from the mains transformer. Am I correct?

My testing shows that I have the correct voltages on all the right pins,
including -15V. However, the LED on the H745 (-15V) does not light. What
does this mean?

-- 
Jeffrey Sharp

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From: Peter Turnbull <[email-masked]>
Date: Thu Mar 6 01:37:01 2003

> including -15V. However, the LED on the H745 (-15V) does not light.
What

It probably means you have one of the ones with an incandescant bulb,
not an LED, and the bulb has burnt out.  That's a common problem, and
easy to fix by replacing the bulb with an LED and dropper resistor.

-- 
Pete						Peter Turnbull
						Network Manager
						University of York

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From: [email-masked] (Tony Duell)
Date: Thu Mar 6 13:51:01 2003

> of front vs back views, and thus I had my regulator positions backwards. We

Wait until you sart populating a large backplane of flip-chips like an 
RK11-C or worse a DX11. The printsets show the backplanes from the wiring 
side you seen. Took me a bit of time to figure that one out (as in 'Hey, 
why are all the PCBs in the wrong slots??').

> finding those voltages on the backplane power connectors!

Yep.

> from the mains transformer. Am I correct?

I believe so. I've never had an 11/34 with the battery backup option though.

> including -15V. However, the LED on the H745 (-15V) does not light. What

The 'LED' runs straight off the output rail, so there's little that can 
go wrong if the output is somewhere near -15V. Most likely you have one 
of the older H745s with a light bulb not an LED, and the bulb has failed 
(they do this from time to time ;-)). Or I suppose if you have an LED 
that, or the series resistor, could be defective.

-tony

---

From: Jeffrey Sharp <[email-masked]>
Date: Thu Mar 6 21:42:00 2003

On Thursday, March 6, 2003, Tony Duell wrote:
>> I got confused by the print set on the representation of front vs back
>> views
>

Thankfully, I already figured that out! I can imagine that causing all sorts
of problems, including much let-outage of magic smoke.

> Most likely you have one of the older H745s with a light bulb not an LED,
> and the bulb has failed (they do this from time to time ;-)).

That is probably exactly what is going on. Thank you and Peter for the
information. If all goes well with other things, I'll be testing the CPU,
memory, and console serial line this weekend.

-- 
Jeffrey Sharp