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

Eric Smith spacewar at gmail.com
Mon Sep 17 17:19:33 CDT 2018

On Mon, Sep 17, 2018 at 1:30 PM, Henk Gooijen via cctalk <
cctalk at classiccmp.org> wrote:

> As far as I know, the 11/40 uses only one H745.
> And vague memory seems te recall that the -15V brick is an “odd one”,
> because, unlike all other bricks, it needs the +15V from the regulator that
> is inside the H742 block. But I could be wrong ...

The D and E position regulators in the H742 of an 11/40 can be:
* both H745, if no MM11-U core memory is used
* one H745 in D and one H754 in E, if some core memory is used
* no H745, and two H754 in D and E, if a lot of core memory is used

The A, B, and C position are always H744 (+5V 25A).

I'm not clear on the distinction between "some" and "a lot" of MM11-U core
memory. It might be explained in the 11/40 manual, or one might have to
work it out from which memory backplanes are powered from which regulator

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