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2007 09 02 Initial Powerup


The power supply capacitors have all been reformed, with the total times as follows:
CapacitorValueVoltageTotal Time
C322 mF50V4h
C418 mF25V1.5h
C580 mF15V2.5h

The "total time" refers to the amount of time that power was applied to the capacitor, not necessarily the amount of time it took me to do the work.

To reform the capacitors, I cycled them several (probably around ten) times from 0V to nominal rated voltage through a resistor that limited the current to 5 mA. The voltage used was about 10% higher than the nominal (e.g., for the 15V capacitor, I used 16.5V). See here for details about capacitor restoration on the PDP-12 (note that in this case I used a variable DC power supply, and not the zener diode ladder mentioned when I did the PDP-12).


Time for a smoke test. I put the power supply on a bench, and got a really long cord. I turned off the keyswitch, plugged the cord into a power bar, and turned it on for one second and then off. No smoke! I felt around to see if anything got hot -- nope. Next, I turned it on for 10 seconds, and then off. Same as before, no smoke, nothing got hot. So, I turned the keyswitch to "ON", and repeated. Everything was fine. Emboldened by this, I measured the voltages on the various power supplies. Everything was perfect:
ExpectedMeasured
+8V+11.79V
-30V-37.7V
-15V-18.8V
+5V+5.17V

Note that the +8V, -15V, and -30V power supplies are really just the raw outputs from across the big capacitors I just reformed (C5, C4, and C3, respectively). So, I expected those to be a little high with no load. The +5V regulated supply, however, was bang on -- +5.17V is perfect.


2007 09 04 Power Supply Wiring


Minimum Quantities of Wiring Required S M L XL

Since the power supply wires had cleverly been cut, I decided to go out and buy new wires. Try finding all the right gauges and colours! And, try buying just one or two meters. "Minimum quantities", my friends. Sheesh! (Any resemblance to the Olympics is entirely coincidental.)

Anyway, the rest of my parts (front panel and spare cards) should be arriving any day now (they were shipped mid last week).


2007 09 06 Arrived!


Extreme Packaging or What! S M L XL

The parts have arrived. The guy really outdid himself in the packaging this time. The front panel was in a custom-built box, along with some of the spare cards, and another custom built box held the rest of the spares.

Stack-o-Spares S M L XL

This is the stack-o-spares that arrived over the two boxes; three core planes, and a bunch of cards that I just didn't have in inventory (and some spares of cards that I did have but went to quantity zero with).

The Front Panel S M L XL

This is the front panel; some of the plastic keyswitches had fallen out during shipping, and the plastics are definitely faded. Luckily, I have two and a half PDP-8/E spare front panels; and I believe the plastics (and indeed the switches themselves) are interchangeable!


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