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The Restoration of the PDP-12 Minicomputer (PAGE 4)


Backplane Cleanup -- 2007 09 14


PDP-12 Empty Backplane S M L XL

Well, now I'm committed :-) I've emptied out the backplane, and inventoried each and every card. Only cards that had some kind of adjustment (e.g., M360) had their locations on the backplane recorded, all others were simply assigned incrementing serial numbers and put on the "to wash" pile. Serializing the cards allows me to track defects and repairs using a "database" (ha ha, a text file).

The reason I track adjustable cards is so that I don't have to "recalibrate" the entire machine; i.e., there's some hope that the settings might just work. Putting my wishful thinking another way: I'm sure that some of the cards will have the correct values, so I'm thinking this will be a better potential for working than if all the (adjustable) cards had incorrect/random values.


Laundry Day -- 2007 09 16


PDP-12 Laundry Day Cards In a Tub S M L XL

Not something you see every day. 340 or so cards sitting in the laundry tub in the basement. I simply let them soak for about 1/2 hour, and then hosed them down individually. I did all the cards except the ones with adjustments, because those ones were most likely not hermetically sealed against water (potentiometers, and all that).

PDP-12 Laundry Day Cards Drying S M L XL

Once the cards were cleaned, I placed them on three picnic tables outside to let them dry in the sun. About an hour and a half later, all done.

PDP-12 Laundry Day Cards Drying S M L XL

Another view of the drying, from the 2nd story window. This picture can also serve as a smart-alec response to, Question: "What's a PDP-12?" Answer: "5 square meters of printed circuit boards" :-)

So, all that's left now is to clean the contacts and the backplane contacts and test the cards. I'm kind of vascillating right now as to whether I do a full 100% test before installation, or just plug all the cards in and power it up and see what happens...


Connector Cleanup and Reinstall -- 2007 09 17


So, today was spent cleaning the backplane connectors with spray-on "contact cleaner" and plugging all the cards back in. It sure helps to be able to take the module locator and sort it based on module-by-location. This way, when you reach into the random pile of boards and pick up an M113, you can see where that one goes. Then you cross it off the list of M113s, and reach for the next random board. And, no matter how organized you are, there are boards left over. In a few cases, I guess I picked up the board, crossed it off, and then decided not to install it after all (perhaps I got interrupted). In one case, I was looking for an M166 at K08 that never existed; it was an M160.

Even so, with removing the cards, washing them, cleaning the backplane, and reinstalling the cards, it was close to two days worth of work.

I guess I've opted for the "plug them all in and smoke it!" approach.
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