my corner of cyberspace =Dan Roganti

PDP-8 Clone: Making the Card rack and backplane —

In here I outline the steps I used to make a homebrew card rack and backplane for my new project, PDP-8 clone (with Transistors). Below you see a series of pics which shows you the various pieces I cut from stock aluminum beams I purchased at Home Depot. Each of the pics have links to see the full size.

In this 1st pic, I measured the length for the rack ears. I need to build a 4U size rack to hold the backplane.  This is made from aluminum stock 1-1/2″ x 1/8″. The length of the rack ears are 7″. This is 1U(1.75″) times 4 spaces. The ears are actually 1/16″ less to accommodate more shelves on the same rack.


The backplane needed some extra space to account for the beams. This is constructed like an erector set around this backplane. It would barely fit in a 3U rack, so I had to go with a 4U rack. So the shelf will seem to have some empty space once it’s mounted on the 19″ rack.


In this step, I measured the braces that are bolted on the top and bottom corners of the rack. They are 6-5/8″ long. These run from the front to the back of the card rack. Two are for the top and two for the bottom. These are made from aluminum stock 3/4″ x 1/16″.



On here, I measure and cut the beams that from side to side. The set in the back also hold the backplane connectors. The length of the beams here are 16″.  The pair which are mounted up front are positioned near the edge. This is so the card ejectors have a leverage point when you pull on them to eject the card. These are made from aluminum stock 3/4″x 1/2″ x 1/16″


Here’s a closeup of the backplane beams. These have to be measured and marked where to drill the mounting holes for the 16 slots. I made a generous spacing of 1″ for each slot. Because I have to take into account the transistor height on the top of the circuit board and the wiring on the back.



Here, I start to assemble the backplane section. I bolted one of the edge connectors to the beams for the back end of the card rack.




In this photo, I have the backplane connectors bolted on to setup the frame for the back end of the card rack. I predrilled the mounting holes for each slot. So then I’m ready to mount the remaining connectors once I get more in the future. I use a spacing of 1″ for the card slots. This gives me a total of 16 card slots per card rack.


More closeup photos of my work here will be posted soon. So then you can view how everything is bolted together.

You can see the current work and pic of the card rack here in my other post.

Categorised as: Electronics | Hobbies | PDP-8 clone | Transistor Logic | Vintage Computers

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