PDP-8 chase the lights

[Evan Koblentz]

Our group here in NJ + surroundings now has monthly-ish repair workshops 
(vs. a few times per year before). At the workshop this past weekend, 
David Gesswein continued restoring our PDP-8.

David summarized: "I fixed the known fault of accumulator bit
going to zero when it was rotated left. This was a bad diode on one
of the accumulator boards. I also replaced two bad bulbs and a third
that died during the repair. Since one that died was one I previously
replaced I'm going to use the not quite matching bulbs with heavier
wires for future repairs. The wires are just too thinn on the 1762 bulbs
and now that they have aged they break too easy. I then found that the 
teletype interface wasn't working and replaced a diode on a R220 to fix 
output. Input is not working properly. I have traced it to a particular 
flip flop on a R220 where when the data changes it feeds through to the 
output without the clock active. I ran out of time to identify the 
component that needs replacing."

Here's a little video of the computer chasing its lights. :)

http://www.vcfed.org/evan/pdp8lights.mp4