Hello Ethan,
(M720 circuit diagram)
>
> That's OK. Al Kossow sent me a copy. It's in his scanned docs for the
> PDP-12.
And it's certainly better quality than what I got from the fiche reader
screen. In case somebody else wants to try: I got readable quality with
a few simple measures. In a dark room to avoid reflections, set the
camera's shutter control to "dark night mode" and put the camera on a
tripod. Since mine doesn't have a remote trigger capability, I used the
timer function to avoid touching the camera, so it would be steady while
taking the picture. For my setup, it didn't make a difference in the
final picture whether I set the fiche reader to "high" or "low" light.
Even though the picture gets darker towards the corners, in a 1,600 by
1,200 (2M pixel) .JPG you can read about everything that is readable on
the screen.
>>As far as I can remember from looking at the fiche yesterday, there are
>>three SN7400N chips and one SN7460N in the circuit, together with four
>>transistors, a couple of diodes and passive parts. Doesn't look too
>>complicated.
>
>
> Nope... it looks pretty straightforward. All I need are some 7460s. :-)
These are certainly harder to get than the 7400s, but it appears to me
that the 7460 is actually used a a kind of delay line: since all inputs
of each gate are tied together, there is no logic function involved, so
maybe you can get away with something completely different.
Since I had the fiche looked up already: the only difference between the
original schematics and Rev. A is C7: it had ".005MFD" originally and
was changed to ".02MFD" in Rev. A. Looks like the one-shot made from E3
needed a longer trigger pulse.
> Thanks for looking, though.
>
> -ethan
You're welcome! - I also used the opportunity to test what the camera
can do for me. Now that I have the procedure: If you need anything else,
let me know.
--
Andreas Freiherr
Vishay Semiconductor GmbH, Heilbronn, Germany
http://www.vishay.com
Received on Thu Jun 12 2003 - 05:09:00 BST