PDP-11/34 PSU Yet Again

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Wed Mar 5 16:38:00 2003

> 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.

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
Received on Wed Mar 05 2003 - 16:38:00 GMT