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Building a New-to-Me PDP 11/23

ajacocks

ajacocks

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I picked up a fairly nice, but empty, PDP 11/23s (BA11-M) chassis, with a backplane and a power supply, at the last VCF swap meet:

BA11M.png

To build out that chassis, I have acquired a DCJ11 CPU:

DCJ11-AC.png

An Emulex UC-07 SCSI controller:

UC07.png

And for temporary use, until I have vintage qbus boards, I built a Qbone:

Qbone.png

Next, I need to power up and check my power supply and backplane, and teach myself to wire wrap so that I can update the backplane to support 22bit cards.

What an introduction to the PDP-11 this will be. Any advice cheerfully received!

- Alex
 
Hi Alex,

That should give you a lovely little PDP. The Emulex cards a great but becoming increasingly hard to find. I guess a nice little Async card would be next on the list?
Something like an DLVJ1-M, (M8043) would be a good place to be. They seem quite plentiful.

All the best,

Andy.
 
Hi Alex,

If you want a DLV11-J (or two) let me know and I will put some in the post for you free gratis...

I also have some National Semiconductor Quad height memory cards.

Dave
 
Very nice little system. Seems like a next logical addition would be a SCSI2SD card to go with your UC-07.

Once the system has a SLU board, such as a M8043, I find it convenient to direct wire the console back into one of the Qbone serial ports so that I can access it via remote login to the beaglebone (using ssh). Makes it convenient to work with the system from other rooms in the house. You can do this trivially using two 10-pin IDC connectors and a ribbon cable with a flip in it:

PXL_20210919_033756194-small.jpg

You might also want to look into getting a grant continuity card such as a M9047. I find the board spacing with the Qbone to be too tight for comfort, even with the mylar sheet included with the kit, which I'm constantly worried is going to fall out. Placing the Qbone with a M9047 between it and the previous card neatly avoids any inappropriate electrical contact,

ragtag-1173.jpg

I hope you enjoy your new system.

--Jay
 
Thanks, Jay. That grant continuity card sounds like a great idea. I found one for $20, and ordered it. Next, I need to strip down my PDP-11/23s chassis and clean it thoroughly. Then, I can get started with checking the backplane and the power supply.

- Alex
 
Oh, thanks, Jack, I didn’t realize that I was buying from you! Thanks again for the HP 86...it was fully working, by the way: the video connector was just oxidized enough to not make contact with an RCA cable, even though my probes did.

- Alex
 
So, I've done a complete tear down and check out on the power supply of the BA-11M chassis:

IMG_1829.jpeg

The power supply was absolutely full of dust and leaves. I cleaned it out with an EM safe blower, and powered it up, where I was able to verify that both +5Vdc and +12Vdc are present and properly adjusted. I'm honestly shocked, as it seems obvious that this chassis hasn't been powered up in a rather long time.

Here's the machine, re-assembled, still with no cards installed:

IMG_1837.jpeg

You can see that the "DC ON" light is lit, and the switch is on. My next step will be to repeat the disassembly and attempt to wire wrap the backplane to upgrade it for 22 bit support.

Thanks to all the folks who have offered advice or parts for this machine. Your help is very much appreciated!

- Alex
 
On a separate subject, has anyone seen any 3D printable qbus card guides? I'm missing one, one is just hanging on by a single post, and several of the others are looking quite frail. I've heard that someone might have created a design.

- Alex
 
Alex,

I may have some spares in a 'cannibalised' system I have in the garage. I'll take a look tomorrow.

I will let you know the 'sorry saga' sometime... It involves a QBUS backplane and a lunatic with a hacksaw!

Dave
 
Vince,

Yep, I was indeed looking for those! I appreciate your work on those guides. For some reason, when I looked at your site using Microsoft Edge, none of the thumbnail images rendered. So, I completely missed your card guides.

For some reason, the spacing on the clips in my BA11-N chassis is different from that in your PDP-8/A. The card guides themselves would work perfectly, but the clips are in rather different locations. Given that, I took one of my broken guides and modeled a new (more robust) guide, and will be uploading it to Thingiverse. You are more than welcome to share it on your site, as well, as you seem to have done a ton of work modeling components.

The guide snaps in correctly to the chassis, and is significantly stronger than DEC's originals. Here is my guide:

Card_Guides_2022-Mar-17_05-29-03AM-000_CustomizedView18057463148.png

I have also attached the STL and the STEP files for the guide to this post.

- Alex
 

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