W076/M452 replacement cards

From: vrs <vrs_at_msn.com>
Date: Wed Nov 26 20:28:41 2003

> > > Is there a good reason for not fitting the reader run modification
> > > (basically a relay) to your ASR?
> >
> > I could do that if I had one, and knew how :-). Repairing my TTY (needs
> > repairs) and adding reader-run are on my list of things to do, but no
where
> > near as urgent (in my mind) as getting these cards tested.
> >
> > One of the repairs needed on the TTY is to get the reader reliable
enough to
> > load programs. Until then, reader-run isn't too important for it,
except in
>
> I have _never_ really liked the ASR33's reader. It's slow, it's not kind
> to tapes, and the contacts are not that reliable, even wben newly set up
> as per the manual. If you're serious about paper tape, get a 'high speed
> reader' The DEC PC04 or PC05 (which you need depends on the machine, the
> latter can be turned into the former -- I've done it) aren't too bad, but
> they're still sproket fed (and thus can tear tapes). The UK-made Trends
> are really nice readers (a lot turned up surplus about 15 years ago, I
> grabbed all I could find!).

I have a PC04. The point here is not to create an optimal tape reading
environment; it is to test whether the W076 replacement card is or isn't
generating this signal with sufficient drive to close the reader-run relay,
if one is present. (I actually intend to load most of my images over RS-232
from a PC.)

> > Is it that easy to mod the TTY? Where do you get the relay?
>
> The instructions for doing this are in at least one DEC printest, similar
> instructions are in the Intel MCS8i manual, and doubtless elsewhere.

I found them. I'd still need relay part number 4915. There are also some
things called "thyractors" called for.

> No idea where you'd get the relay these days. I wonder if you could
> design a solid-state switching circuit that would work, with an
> opto-isolator on the input

Maybe, if I had specs for the relay. If I had the specs, I might even be
able to tell if I have a prayer of delivering sufficient drive current,
though I'd still prefer to test on real hardware before having a bunch of
boards manufactured.

    Vince
Received on Wed Nov 26 2003 - 20:28:41 GMT