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DEC H3171-A RS232 Distribution Panel

Mal

Experienced Member
Joined
Apr 3, 2008
Messages
91
I'm looking for a neat way to put a row of 4 x DB25M connectors inside the back of a corporate cabinet that houses my 11/23 system.

I found a H3171-A RS232 Distribution Panel that looks to be perfect for this (see pictures).

h3171-1.jpgh3171-2.jpg

But the cabling has me stumped.

On the back of the H3171 is a 40-pin berg-style connector. I have a 40-way ribbon cable that has a 40-pin header at one end and 4 x 10-pin headers at the other end. Sounds perfect for connecting this to a 4-port DLV11-J, right? I've buzzed it though and the problem is that the top and bottom rows are interposed. So this straight through cable doesn't work. It's as if every pair in the 40-pin cable needs to be swapped (eg 2-1, 4-3, 6-5, etc).

Has anyone used the H3171 with a DLV11-J? If so, do you have any tips for wiring this thing up?

I'd also appreciate any pointers to technical documentation for it. I've not found anything on the web or in the DEC handbooks I have.

Thanks.
 

gslick

Veteran Member
Joined
Dec 30, 2010
Messages
2,112
Location
Seattle, WA
In this picture it looks like the 40-pin cable that splits into four 10-pin headers attaches to the back of a 40-pin bulkhead connector, shown flipped down here. Then maybe the 40-pin cable that connects from the other side of that bulkhead connector to the H3171-A distribution panel results in the pin swapping, if that is necessary.

http://www.physics.purdue.edu/~jones105/pdp-11/
http://www.physics.purdue.edu/~jones105/pdp-11/images/IMG_2881.JPG

IMG_2881.JPG
 

Mal

Experienced Member
Joined
Apr 3, 2008
Messages
91
OK, thanks. That makes sense now. The bulkhead connector (or lack of!) is what's causing the pin swapping problem. My BA11-NC chassis is a little different to the one shown in the picture. Mine doesn't have the flip-down hinged bulkhead panel. It was either never there, or has gone missing. I'm contemplating doing a cut and splice of the cable so I can wire the H3171-A direct to the DLV11-J. Or find a different DB25 panel.
 

Mal

Experienced Member
Joined
Apr 3, 2008
Messages
91
I added an improvised bulkhead connector. That fixed the pin-swapping issue.

The 11/23 is humming along nicely now with the VT320 console on Ch3, TU58 emulator on Ch0 and Letterprinter 100 on Ch1.

It's nice to finally have a system in a cabinet rather than strung together between shelves!

Here's a couple of pictures:

cabinet-rear.jpgh3171-bulkhead-connector.jpg
 

gslick

Veteran Member
Joined
Dec 30, 2010
Messages
2,112
Location
Seattle, WA
Is there a part number on the 40-pin to four 10-pin cable? Don't see too many of those. A part number would be helpful if someone wanted to try to find one.

Nice that you found a simple solution.
 

Mal

Experienced Member
Joined
Apr 3, 2008
Messages
91
I don't have the part number unfortunately. I have one cable that appears likely to be a DEC original cable (it has Berg-branded connectors on it), but any label with a part number on it is long since gone.

Here's a picture of it (it should be easy to fabricate using normal IDC connectors).

4-to-1-cable.jpg

Note that the cable pin 1 (red stripe) connects to pin 10 of the left-most 10-pin connector. That's the only unusual feature of this cable.
 
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