DEC PDP-11/45 backplane +5 ECO

[Josh Dersch]

On Sat, Apr 24, 2021 at 1:36 PM Fritz Mueller via cctalk <
cctalk at classiccmp.org> wrote:

> Hi Josh,
>
> Among the pictures linked from your message about the H742a parts, there
> is one picture of you backplane.   I have been looking for some time for
> information about the following 11/45 ECO:
>
> > KB11-00001 CODE: D May-72 [ECO]
> >
> > Problem: Etch carrying +5V current from Mate-n-Lock pins to backpanel
> pins is not heavy enough to carry required current. Correction: Run 24AWG
> wire in parallel with etch on panels which already have Mat-n-Lock assembly
> installed. Increase thickness of conductor with solder bead if Mate-n-Lock
> assembly not installed. PDP-11/45 system serial number 101 and later.
>
> The wiring arrangements at the top of your backplane look to be a bit
> different from mine, and I believe you may have this ECO implemented.
> While you have your backplane out, could I ask that you take some closeups
> around the Mate-n-Locks along the top?  I'd be very interested to see the
> board traces and the details of the red bus wiring there.
>

For sure.  I have it on a shelf in the garage to keep it relatively safe
while it's out of the chassis, next time I'm out there I'll take some
pictures.


>
> Pictures of the toasted 11/45 suggest that the original machine had the
> older power wiring scheme (distribution panel mounted vertically on back of
> cabinet instead of horizontally at top of cabinet, etc.) although your
> KB11A serial number badge is >2000, which is curious...


Yes, I was looking at the service docs and it does seem to match the
earlier wiring scheme.  If you have notes on re-creating the harness, let
me know.  The molex shells actually survived the heat (with a couple of
exceptions) so I should be able to reuse them. Looks like I'll just need to
order up a ton of wire and pins (and a crimper, probably).

I'll get the 15V boards out of the H742's this week.

- Josh