MicroPDP-11/23+ cabinet kit cables

Douglas Taylor dj.taylor4 at comcast.net
Thu Jul 25 21:32:44 CDT 2019

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.

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