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Need to see the connector arrangement of a cable

NeXT

NeXT

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Joined
Oct 22, 2008
Messages
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Location
Kamloops, BC, Canada
Having trouble getting a known good RQDX1 and RX50 to behave, I suspect my home made ribbon cable is at fault even though it tests fine.
It was built to replace a BC02D-1D ribbon cable (runs from the controller to the drive distribution panel in a BA23 eclosure).
My home made cable is passive (pin 1 on one end is pin 1 on the other) but because of this, the cable has to fold over, otherwise on one of the sides pin 1 will be lined up with Pin 50. The fold in such a small case does not feel DEC-like. Can anyone confirm that I don't in fact ahve one of the connectors on reverse (and I should really have pin 1 on one side translate to pin 50 on the other).
 
With an RQDX3 in a BA23 the 50-pin ribbon cable runs flat from the controller under the backplane and distribution panel and into the distribution panel without any twist.

Without checking I would assume that the same would be true for an RQDX1, but I have never seen an RQDX1 or RQDX2, only the RQDX3.
 
This figure does not show any twist in the cable between the RQDX1 and the BA23 distribution board. (Although it does show the cable plugged into the back of the board instead of going underneath the board and into the front. Maybe that is just artistic license to make the connection easier to see and/or draw.)

http://www.bitsavers.org/pdf/dec/qbus/EK-RQDX1-UG-001.pdf
RQDX1 Controller Module User's Guide
Page 3-4, Figure 3-4 RQDX1 MICRO/PDP-11 Signal Distribution Connections
 
Perhaps these will help....

DSCN5018.JPG


Above photo is obvious...

Lower photo is taken from the rear of the access bay, with the panel removed. The cable does not "flip".... the red bar of the cable is away from the BA23 edge with the FANS.

DSCN5020.JPG


Both cable ends are made with standard strain reliefed 3M connectors, pin 1 on the red bar. [shown in the last photo]

Oh, and RQDX1, 2, and 3 use the same cable.
 
Nice pictures. That should make things completely clear.

So instead of twisting the cable DEC twisted the connectors. The red stripe of the cable will only match the normal Pin 1 location on either the controller or the distribution panel, but not both at the same time.

In your picture the red stripe of the cable is plugged into the left end of the distribution panel connector while the triangle indicating the standard Pin 1 location is on the right end of the distribution panel connector.
 
gslick said:
Nice pictures. That should make things completely clear.

So instead of twisting the cable DEC twisted the connectors. The red stripe of the cable will only match the normal Pin 1 location on either the controller or the distribution panel, but not both at the same time.

In your picture the red stripe of the cable is plugged into the left end of the distribution panel connector while the triangle indicating the standard Pin 1 location is on the right end of the distribution panel connector.
Click to expand...

Yes Glen, the cable plugs into the RQDX in the correct orientation [Pin1 / BAR on the PCB connector ARROW] but is "reversed from normal" at the bulkhead end. [shown clearly in the first photo above.]


I didn't do it, I just report it. :crazy:
 
Why an RQDX1 and RX50 instead of a slightly more useful RQDX3 and RX33 (or equivalent)? Is part of the goal to stay more true to an original configuration, or is it simply the hardware you happen to have on hand?
 
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