TTY 33 - Finally

Christian Gauger-Cosgrove captainkirk359 at
Fri Jul 3 22:21:23 CDT 2015

On 3 July 2015 at 21:50, Rick Bensene <rickb at> wrote:
> Hello, all,
> Today I received a very nice, (mostly) operational Teletype ASR-33.  It is in really stunning cracks, very little discoloring, everything is there, and the best part is that it is very clean inside, and it works great as far as I can test it in local mode, except for one thing:
> The paper tape reader has a problem.  Put a tape in, clip down the cover (not this is all done in LOCAL mode), and press the lever to START, and the tape reads one frame, prints the character, the reader stops, and the printer acts like it is receiving a BREAK signal...just free-runs without printing anything more.  Only way to stop it is to power it off, then power it back on again.
> I know there is the Green Keys list, but I'm not a member (though I probably should be now), but knowing the knowledge base of folks on this list, I figured I'd ask here first, and see if anyone has any ideas.
Congratulations on getting a nice 33ASR! Yeah, still you should hit up
the Greenkeys list:

Just never discuss what oil to use.

> I'm wondering if perhaps TTL or (I'd never get so lucky) RS-232 signals are used for the coupler.  I haven't taken the cover off the unit yet to determine if how the cable is connected into the terminal, as I'm really itching to hook this thing up to my PDP 8/e and do some "period-correct" computing.   If the terminal only does current-loop, I think that I can make a cable that'll work with the serial card in the 8/e to get the terminal going (I seem to remember the serial card (can't remember the M number) can do both current loop and RS-232), but if the TTY could easily do RS-232, then it'd be a snap to hook it up.
> Last week I did order a nice little Black Box Current Loop to RS-232 converter, which will make things easier, but it'll be a few days before it gets here.
Not seeing it, or the modem, that six prong cable from the Teletype
itself is probably current loop. What four pins for the actual loop
(RX+, RX-, TX+, and TX-), the other two I guess could be power for the
modem if it doesn't have an external supply. (Or they could be

Unfortunately to connect it to your PDP-8/e, you would need to modify
the Teletype according to DEC's LT33 modifications. Most of which has
to do with putting the reader under computer control. Dave Gesswein's
site I believe has a scan of the manual/printset/thing I believe.

> Fortunately, the TTY also came with original Teletype technical docs, so once I get it open, I should be pretty easily able to figure things out.
That's excellent. Still, Greenkeys list for all things teleprinter.
They'd probably also be able to help with making the machine usable
with your 8/e as something other than a remote terminal.


P.S. The proper nomeclature is "33ASR", not "ASR33". "Teletype Model
33, Automatic-Send-Receive" is better sounding (and seems more
grammatically correct) than "Teletype Automatic-Send-Receive Model
33". Though, I believe we can blame DEC for swapping the the model
number and "type" (ASR, KSR, or RO) of the Teletype machines. Since in
the PDP-4 brochure on BitSavers they say "KSR28". If I recall
Christian M. Gauger-Cosgrove
Contact information available upon request.

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