Desperately need BA11-N/BA11-S Technical Manual

Noel Chiappa jnc at
Wed Sep 16 08:36:57 CDT 2015

So, I'm trying to fix a broken Power Monitor Boards (the thing that drives
ACLO/DCLO) in an H786 (BA11-N power supply), and although I have the prints,
I can't make head or tail out of them.

(The circuit is a maze of op-amps and 555's. OK, OK, so maybe an analog guy
can take one quick look, and understand instantly how it works. But I don't
have that gene! :-)

So I'm looking for a BA11-N or BA11-S Technical Manual, to explain it to me
(my experience is that the DEC Tech Manuals for power supplies are _really_
good at that).

(Either the BA11-N or BA11-S since, although the PM boards have different
part numbers in the two - 54-12528-0-1 in the BA11-N/H786, and 54-15048-0-1
in the BA11-S/H7861, the circuits in the two seem to be pretty much
identical, looking at the prints.)

Alas, neither seems to be available online. (The BA11-N is EK-BA11N-TM-001;
the BA11-S is in the "PDP-11/23B Mounting Box Technical Manual",

I have clues to the existence of a couple of copies of the BA11-N one,

A "David Powell" (then at ICUKnet in the UK) sent out a message saying he had
one, but the email address for him at ICUKnet no longer works - I haven't
(yet) tried to find him via LinkedIn because it's a common name. I don't
suppose anyone here knows him, do they?

Also, this page:

which claims to be the "Book Catalog (incomplete) of the Computer History
Museum, as of July 27 2002" says they have one. Would it still be there,
and is there any chance that, if so, it can be scanned an put online?

Many thanks, in advance, for any help with this - I'm pretty desperate!


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