#31 (Rack Configuration) is alive and well. All the LEDs, Switches and diodes worked perfectly.

It took me a few hours every day for about a week to build the rack configuration. Every time I came across a confusion or needed to research something more carefully, I took notes in case a clarification or correction might be of general use. Here are the notes.
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“Add 5 more resistors” should read “Add 4 more resistors” (find the 5th resistor whose name is Waldo!).
Section 3. Test the PiDP-1 to see if everything works
When run, the test program at /opt/pidp1/test.sh displays:
“If all switches are set UP and RIGHT”
It should display:
“If all switches are set UP and LEFT”
Equipment issues
Was short 4 x 1N4148 diodes - I used 6 surplus from old PiDP-11/70 kit, keeping one controller fully populated with old-kit diodes… they worked just fine.
A couple of boards were not pre-separated (e.g. Ottopanel (Ref. #9) and Ref. #10). Not difficult to do manually.
Why are 6 plastic wire protection DE-9 sleeves included. DE-9 for space war controllers just needs 1.
8 Red switches: 3 of them came with 3 nuts, 5 of them came with 2 nuts. Did not have enough nuts to start with to populate all 8 with 2 internal and 1 external. No biggie, I used 1 internal and 1 external per red switch. Now I have 5 surplus nuts. Too many nuts work here, anyway!.
Section 5. Build the game controllers
(1st instruction line says) “Start with cutting the supplied cable into two pieces, one for each controller”…Nope…. Don’t cut the supplied cable if two are already in the kit (as in mine)!
In the section titled “The DE9 connector on the other end of the cable”. To the right of the last open DE-9 picture, the large block table that gives all colors and pin assignments
Colors assigned in the middle block diagram are wrong, colors used in big block diagram do not match the two smaller blocks below it (for Controller1 and Controller 2), or “Back side” color assignments shown in a picture a few above it (in “The two controllers” section).
Largest Table should contain the following associations:
Red = row: pin 1
Green = fire: pins 5 and 9
Yellow = thrust: pins 4 and 8
White= right: pins 3 and 7
Black = left: pins 2 and 6
There are 2 Ref. #K, Ref. #L printed items. Ref. #K and Ref. #L, that are needed earliest, are hidden as punch-out items on speaker frame (the other two label duplicates are the badges but it’s quite confusing to find these earliest and it’s not obvious the correct two pieces require more searching).
No reference is found for the use of the 2 church-window shapes and 6 oval tabs punch-out blue plastic on the speaker frame (Ref. #N). There’s a visible hint in a couple of pictures that the church-windows are used to link the speaker section to the racked main console below it. Using the oval tabs under the 6 remaining black metal screws between the sound panel facia and the foam, get in the way of the T-bar separation spacing. Ultimately I did not use the oval tabs at all.
In: https://obsolescence.dev/pidp-1-rack-building-instructions.html
Open section titled: “Use three of the four aluminum profile to construct a U-shape” the caption of the first picture in this section says:
“Not shown are the 4 stand-offs that can be mounted to the back of the profiles, and the 5 T-bar separators that go between each of the panels.”
That’s was very cruel as only 4 T-bar separators are supplied. I panicked until I cross referenced the package contents in: https://obsolescence.dev/pidp-1-building-instructions.html
(section “Additional Parts List for the PiDP-1 Rack version”) which states “4 aluminum T profiles (spacers between panels)”.
That's it for now... back to playing Spacewar!
(Thank you, Thank you, Thank you, Oscar and crew).