On Apr 24, 2021, at 7:02 PM, Josh Dersch
<derschjo at gmail.com> wrote:
If you have notes on re-creating the harness, let me know.
A few pointers -- I think I left some of these in a comment on one of your
fb posts, but will repeat here in case others may find it useful:
* The wire list in the commonly available Jun74 11/45 engineering drawing
set is actually for the power harness, and not for the backplane. It
includes wire run lengths in inches, which is quite handy. I believe it is
for the newer harness, but there is much overlap.
* The old and new harnesses are also schematically illustrated on four
pages of the drawing set marked "power systems configuration". These
drawings are complete and quite good.
* Drawings for the power distribution board for the older wiring style
(vertical at the back of the cabinet) are hidden in the Jun74 11/*40*
engineering drawings (upper right of sheet BA11-F0).
* What I did was use the wire list lengths as a guide, cutting each run to
length plus a little extra. I then started with the H742s on the bench, at
the regulator and power monitor mate-n-loks. Then put the H742s in the
rack with the CPU cabinet, and worked my up and over the and then down
along the along the backplane toward the console, bundling and trimming to
length as I went.
* A good ratchet lock crimp tool makes a big difference here. You want
one with a die that can handle 14 AWG, and on which will crimp both the
electrical and strain-relief parts of the pins in one go.
* Sticking with the original wire color code also makes it a lot easier
not to get lost and later to double check and troubleshoot your work. I
used MTW ("Machine Tool Wire"), which is available from wirebarn.com
14 and 18 AWG in most of the necessary colors and in 25 and 100 foot
lengths (I think the 18 AWG purple I had to find separately on eBay, but I
have lots of leftover of that and will gladly send you some.)
* I skipped wiring for most of the regulators in the bottom H742 (I have
regulator F there, but none of H, J, K, or L are populated) because I don't
have any core or fastbus memory in my system. I figure I can add this
later if I ever do find myself with either of these.
Thanks! I may get started on that fairly soon, we'll see how ambitious I'm
Sorry for the delay, but finally, here's a pile of pictures of the +5V ECO
on the backplane. Let me know if you need more detail on something: