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The Restoration of the PDP-8/I Minicomputer (PAGE 4)


Basic Powerup


Now that the power supply works, and I had the full complement of cards, and the backplane and other mechanical structure were deemed to be in good condition, it's time to apply power.


Initial power on inspection -- 2003 06 08


Applying power, and trying simple things like loading an address of all zeros and then an address of all ones indicated that things were not fully operational. Some other basic tests, like pressing "deposit" to get the memory address to increment as each word is deposited, also indicated some faults.


Front Panel Bulb Diagnostics -- 2003 06 08


The first thing to do was to get the front panel running. After all, there's so much that you can tell about the machine with a working front panel that trying to diagnose it with a malfunctioning one is plain stupid.

I figured that at least some of the bulbs had to be burnt out. I toggled around on the front panel and tried to get as many of them to light as possible. Whenever I found one that was off, I'd stick a small yellow sticky note piece to it. If I ever found later that the bulb in fact worked, I'd just remove the yellow sticky. On my initial run, I discovered about 35 lights that would not light up. Up went 35 stickies.


Go back and clean the contacts -- 2003 06 08


At this point, I decided that it would probably be beneficial to clean each and every contact on each and every card in the 8/I's chassis. I used rubbing alcohol and paper towel. After I cleaned all the contacts, about 10 more lights lit up -- woo hoo! Away went 10 stickies.


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