Looking for two DEC H445 power bricks for PDP 11/40 project

Noel Chiappa jnc at mercury.lcs.mit.edu
Tue Sep 18 09:27:47 CDT 2018

    > From: Pierre Gebhardt

    > As I don't have core memory modules available, I thought of using MS11
    > memory, which, according to my research, seems to be an option for
    > 11/40 systems. 

Err, which kind of MS11? There are lots of different ones:


and they don't all work in every UNIBUS PDP-11!

Your options are the -E/-J group, and the -L, but the latter are a bit hard
to find, and expensive. (There may be non-DEC equivalents, but I don't know
about them.) They all need a MUD backplane such as the DD11-C or DD11-D.

(IIRC, the -M has a 'UNIBUS' jumper, but the card uses non-standard voltages
on the backplane; 12V instead of 15V, IIRC.)

    > Does that mean that a single H745 regulator might be sufficient for my
    > needs?

If you're not using a lot of MM11-L, you would definitely only need one H745,
no matter what configuration you have. (Note that if you have an old
machine/harness, there's a jumper you have to add if you have only a single
H745; see the second paragraph on page 6-18 of DEC-11-H40SA-B-D.)


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