11/34a power supply/regulator question

[Don North]

dundas at caltech.edu wrote:
> The recent discussion of Julian's PDP-11/34 inspired me to look at an
> abandoned one that I adopted some while ago. The particular computer in
> question is a /34A-DE.
>
> After looking at the prints and checking a few voltages, I find I have
> no +5. Reviewing the recent thread and looking closer at the prints, it
> seems that I am missing two H7441s. (It does have a H754 and H745, with
> the 54-10864-YA [Rev. L] distribution board.) Is that correct? It
> needs (one or) two H744 or H7441 (in my case) in order to operate?

Depending upon how many backplanes you have in your box and how much
stuff in each backplane, you need anywhere from one H744 (25A at 5V) to
two H7441 (32A at 5V each, 64A total).

The first H744(1) will power the 9slot CPU backplane. If you have a true
11/34A with FPP and/or cache module the H7441 is required. A minimal
11/34A (no FPP or cache) can use just an H744.

The second H744(1) slot powers the expansion backplanes. If they are not
present, you don't need it at all. If they are fully loaded, then the H7441
is your choice.

The -YA version of the power distr board is designed to handle the
additional load of the H7441s. It will work with either H744 or H7441.