[GreenKeys] paper tapes and rubber bands = bummer

[Bob McConnell]

Chris Elmquist wrote:
> Yes...  I agree that a non- or minimal-contact approach is the way to
> go for these old tapes.
> 
> The only downside to a home brew optical reader is that you have to pull
> the tape through manually and some of these tapes are really long--  eg,
> 8K BASIC for the 680 is a roll about 5" in diameter with a 1/2" center,
> so you'd be pulling tape for a long time.
> 
> The appeal to the old mechanical reader on the M33 is that it is
> automatic.

If you have anything like a tape winder, you could use it to pull the 
tape through the reader. If you do rig something up, make sure the 
tension is as low as practical to avoid breaking the weakened tapes.

I used to have one of those OP-80 readers, and it had a parallel 
interface. If you used the feed hole rising edge to trigger an interrupt 
or latch the data, they were not speed dependent. That hole is smaller 
but on the same center line, so the data bits have already become stable 
when the trigger occurs. There was an upper limit based on how fast the 
processor could handle the interrupts and save the data, but that limit 
should be much higher now with the faster processors we have.

Different tape colors sometimes worked better with different light 
colors for the illumination. Some tapes were too transparent for white 
light to be effective.

Bob McConnell
N2SPP