Paper tape punch interfacing?

[Tony Duell]

> It won't be punching miles of tape so sewing machine oil will
> probably work in the mechanism (there is a sticker on the Lexan
> cover that indicates the "light turbine oil").

Would you believe I even have a tin of the oil (!). It's the sort of tin 
you open with a can opener, and it's never been used. But I also have a 
Tally 420 that will need it one day.

> 
> >Having built a PC04 (well, converted a PC05 into one...) I seem to 
> >remember that the DEC punch mechanism is a synchronous one. The motor 
> >runs all the time, turnign the camshaft, you get a pulse per revolution
> 
> You recall correctly. I found the PC04/05 manual as well as the
> PC8E interface schematics on bitsavers.org. I think your approach
> to clock the interface card at slightly below the maximum punch
> rate is a good one. I would use a one-shot to "reply" the sync
> pulse to the PC8E but then it wouldn't have any way to start the
> first character.

It's also easier to make a stable-frequency clock than a stable 1-shot...

Thinking aobut this, you might need to trigger a 1-shot off the feed 
solenoid signal coming from the PC8E to provide the right pulse width to 
drive the Tally 420. You can then use the output of that to gate the data 
channel signals. You will need to experiment a bit, of course.

-tony