18 Aug
2008
18 Aug
'08
1 p.m.
I'm
moderately sure that the paper tape I used back when I had a PDP-8
was not symmetric in the way needed here - the line of feed/timing
holes was not on the centreline of the tape.
You are remembering correctly - they are not.
*But*, you could read the tape one way, flip it _and_ read it backwards.
Syncing up the two passes is just an exercise for the student ;-)
Personally, my PC04 is the primary load device for one of my PDP-8/Ls.
I'd be hurting if I lost a phototransistor - the SMT idea sounds handy.
What I'm more worried about is a spare bulb - It's a "festoon" bulb
(the kind commonly used for older automobile dome lights - it looks
like a large AGC-type glass fuse, with an axial filament), but trying
to cross it with a modern one from Osram or others has drawn a blank
for me. Has anyone found a modern substitute?
Is it particularly critical? I can't even remember what the voltage is
supposed to be, but assuming you can find something of the right voltage
and about the same wattage it should work.
Now, finding replacement bulbs for an HP2748 is another matter (that
reader has an individual 'grain of wheat' bulb for each track, all 10 (8
data tracks, feed track, reference lamp) in series across a 45V supply.
-tony