KY11-LB prints, and versions

Noel Chiappa jnc at
Wed Apr 6 08:08:55 CDT 2016

So I'm in the process of repairing a couple of M7859 KY11-LB -11/04-34
Programmer's Console boards, and the existing FM Print Set was kind of hard to
read in some areas, so I looked online for another set, and although I didn't
find one, I noticed several other people with the same issue - asking for a
better set.

My brain did eventually turn on, and I remembered DEC's habit of putting
prints for included devices in with print sets for computers, and with that in
mind, I managed to locate another set in the -11/34A print set; that one is a
lot clearer.

To my surprise, they showed a slightly different board from the one in the
existing FMPS available online: in the later version, the four 8093 quad
tri-state buffers between the UNIBUS data lines, and the internal bus, are
replaced by 74173's. I'm not sure quite what motivated this change - no
documentation that I know of refers to the existence of two different

The PCB is slightly different, but the ROMs are apparently all the same, so
from the point of view of the i8008, the two versions must look the same. (And
given where the change is, it can't make any difference to the interface
between the card and the front panel, CPU boards, etc, so either version
should work anywhere.)

Anyway, the version in the -11/34A prints didn't include the actual front
console, plus to which the prints there had been heavily marked up by someone
at some point. So I have produced a new set of prints:

which includes the front console pages from the earlier set, and a cleaned up
version of the pages from the -11/34A set for the M7859; hope this is useful
to someone!


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