Micro PDP-11/70
Approx. 1/5th scale replica.
Introduction
The PDP-11, introduced by Digital Equipment Corporation (DEC) in 1970, is one of the most influential computers in history. It played a critical role in various fields, from industrial control systems to academic research, and its legacy can still be seen in modern computing principles.
This project is inspired by the PiDP-11 project and depends heavily on their work. The design of this replica is centered around an available LED, with all dimensions approximated to capture the look and feel of the original. Functional aspects are limited to LED feedback, and working switches were not included in the design considerations.
On this website, you'll find all the 3D printable files and a short guide to assembly. The material used was mostly PET-G but any material will do. You can find all necessary files on the right. Most of the design made in TinkerCad some in FreeCad some combined. If you have to make adjustments links to individual designs also available bellow.
The frame
The frame consists of six part. Two sides which are identical. Two shelves, one of them has an opening for cables. And the top and Bottom part. Print them from black material laying flat on the printing bed.
This leg piece was designed with FreeCad and the little circular end was added in TinkerCad leg.FCStd
Print two of these. One must be mirrored.
The leg pieces fit in the opening of the bottom part. They are not scale correct but bigger ones would look ugly. Glue is necessary to hold them in place.
The assembly of the frame is quite easy. Use some glue where necessary. If you seen my video about this build you may noticed that the assembly was wrong there, The opening for cables must be on the left side if you facing the frame from front.
Drawers
These containers/drawers (not sure how to call them) are filling the frame. The bottom (drawer_std) has nothing to do. The back is open for future use. One is to hold a Raspberry Pi and one is to hold the CPU. Print from greyish material in orientation as they on the design.
The front covers were designed in FreeCad. Two of them needed and can be press fitted to the bottom (standard) and to the middle (pi) drawers. For the rim I selected a yellowish material (not sure that is historically accurate). The covers printed facing down without plate adhesion support. Rims the same.
Front cover: std_front_2.FCStd
Rim:https://www.tinkercad.com/things/8ox3qlE0cwN-rim
The rims had to be glued to the fronts. Still not the best fit, you may want to play with the dimensions according to your material and printer.
The drawer for the pi has holes to accommodate it. Unfortunately I screwed up the design so mounting standoffs has to be glued in place.
CPU panel
The most delicate part. Consists from two major parts.
Frame
Nothing special. This will accommodate the front panel and the switches. For best quality print it facing up.
The panel
This panel has nests for 64 LEDs. It is designed for a certain one. 204VD2A-V1-1A
Pet-G is preferred as it flows well and quite flexible. Printing should be done facing down so no support material will go in the nests. If everything gone well the LEDs should snap fit in the nests.
Sticker
To decorate the front panel an Android app were used to generate a pdf. In this app you
can adjust the main colors to match with a material
on hand for the switches. If you seen the short video, you may noticed some errors on
the sticker. These errors now corrected.
The app can be found at:
https://play.google.com/store/apps/details?id=hu.landov.pdpfront
If additional adjustments necessary the source code can be found here:
https://github.com/landov/pdp-sticker
Switches
The best to print them in groups. The material color will define the outlook of the replica. 15 purple 14 red and one white needed.
The switches must be glued in the cavities on the panel.
rotary switch
lock
Definitely there's room for improvement.
The assembled Cpu front snaps to the container.
Electronics
The inner parts of this replica is a stripped down version of the PiDP-11. From the original design all is kept the Raspberry Pi, ,the LEDs and the resistors. The driver ic is gone. With this LEDs the Pi works fine. Obviously there's no switches. With this scale they would be useless, except one. The SW28 Test switch must be spared as a direct connection through a diode, connecting Column 0 with Row 2. (Otherwise all LEDs would light up at once) The Serial RS-232 are also missing at this time. This build uses some universal prototype strip boards.
This board is a segmented strip board. Contains the necessary resistors and a connection to close the test "switch".
This board is a regular strip board distributes the columns. The first pin row sits in the first
board.
This strip board distributes the rows.
A special part holds the pcbs in place. You probably want to redesign it according your boards.
Unpaid advertisement
Key Features:
- Nested Lists.
- Share with friends
- QR Code Reader.
- Customizable Categories.
- Schedule to Calendar.
Side panels
The side panel were covered with furniture foil and simply hanging on the frame. Printing of these may cause issues because their size.
Emulation
https://obsolescence.wixsite.com/obsolescence/pidp-11-building-instructions
The drawback not having working switches is that the desired OS has to be started from command.