PDP-11/45-55 CPU fan assemblies

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat Nov 7 14:54:16 CST 2015

    > From: Tony Duell

    > IIRC that 21" mounting box (and I assume therefore the fan assemblies)
    > was used on other machines like the 11/40 (some versions), the 11/70,
    > etc.

Yes, I _think_ the hardware was identical - I had an 11/40 for a year or two
'back in the day', before I got upgraded to an 11/45, but it's been a _long_
time since I've seen one, so I can't be positive. I tried to find parts
numbers in the drawings, but none of them (11/40, /45, or BA11-F) had them.

    > the bottom one is a right pain, involving removing all the boards and
    > dismantling the very fragile card guides

??? Mine still has the card guides in place, although the bottom fan assembly
is gone?

Thanks very much for the offer of help, but let's see what Henk turns up!

    > From: Henk Gooijen

    > The colors of the /55 are quite different from the 11/45.

Well, I did say that the front console was different! :-)

But other than that, I am pretty sure they are otherwise identical: same
backplane, same CPU boards (although the /45 can be found with both the
KB11-A and KB11-D variants; I _think_ the /55 only comes with the -D), etc.

    > all 21" boxen (BA11-F ?)

My manuals say the 11/40 one is a BA11-FC, and the 11/45 is a BA11-FA. Not
sure what the difference is - maybe it's that the /45 has two H742's in it,
and the 11/40 has only one? Although I guess those are mounted on the cabinet
(although they are in some sense still part of the CPU chassis). Maybe it's
the different power harness/etc?

    > The box is (AFAIR) mounted on the card cage with 4 or 6 (?) screws.

Mine looks like it uses 6.

Anyway, thanks very much, I have my fingers crossed that you will find both
of them when you look! :-)


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