MicroPDP-11/23+ cabinet kit cables

[Glen Slick]

On Thu, Jul 25, 2019 at 7:32 PM Douglas Taylor via cctalk
<cctalk at classiccmp.org> wrote:
>
> On 7/25/2019 10:11 PM, Glen Slick via cctalk wrote:
> > On Thu, Jul 25, 2019 at 10:09 AM Douglas Taylor via cctalk
> > <cctalk at classiccmp.org> wrote:
> >> I'm putting together a MicroPDP-11/23 in a BA23 box.  Have the M8189 CPU
> >> quad width board and the bulkhead cabinet kit, with two DB25 connectors
> >> and switches to set the baud rate.  On bitsavers the 'MicroPDP11 system
> >> technical manual' shows how to set jumpers on the M8189 to allow this
> >> cabkit set the baud rate, but only briefly mentions the cables needed.
> >>
> >> Does anyone here have a anatomically correct MicroPDP-11/23+ in a BA23
> >> box and can tell me how the cabling goes from the M8189 CPU board to the
> >> bulkhead cabinet kit?
> > I might have a console panel for an M8189 KDF11-B 11/23+. If I do, I
> > couldn't find it the first couple of places I looked. Or maybe I have
> > a console panel for an M7554 KDJ11-D 11/53, I forget which one, or
> > both, or neither that I have.
> >
> > Anyway, back to the cable for the console panel for an M8189 KDF11-B
> > 11/23+, isn't that just a 20 conductor ribbon cable that attaches to
> > the 20-pin connector on console panel, then on the M8189 end it splits
> > in the middle into two 10 conductor halves for the two 10-pin
> > connectors on the M8189?
> >
> > To use the baud rate switches on the console panel the M8189 needs to
> > be jumpered for external baud rate generation. The console panel
> > contains a baud rate generator which feeds the baud clock into pin 1
> > of each of the two 10-pin connectors.
>
> Yes, it is a 20 pin cable at the bulkhead.  I appears to be keyed so you
> can't put it in wrong.  The 10 pin connectors on the CPU board don't
> seem to be keyed, so my uncertainty is about how the cable wires go from
> the 20 pin bulkhead to each 10 pin connector. Is there something that
> gives the orientation away?   I thought maybe tracing the Rx Tx pins on
> the DB25 connector to the 20 pin cable, then on to the 10 pin CPU
> connector.  These probably go straight thru without any diversion.

In the photos that I have found of the M8189 console panel there is a
'1' just above the top right of the 20-pin connector indicating Pin 1.
A trace can be seen leading from that pin to the baud rate circuitry.
So that pin would go to Pin 1 of one of the 10-pin connectors on the
M8189.

Then 5 pins over from the Pin 1 on the console panel another trace can
be seen leading from that other pin to the baud rate circuitry. So
that would be Pin 1 of the second half of the cable going to Pin 1 of
the other 10-pin connector on the M8189.