TTY 33 - Finally

Rick Bensene rickb at
Fri Jul 3 20:50:26 CDT 2015

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.

The TTY came with a neat General Electric TDM-114 Acoustically Coupled Data Set.  There's a cable that comes out of the terminal (it's a table top model, not a pedestal model) that has a six-pin connector that plugs into a socket  on the back of the dataset.   The acoustic coupler cups aren't very deep, and are a relatively hard rubber-like material, but there are little spring loaded rollers that are designed to grab onto the handset and press it securely against the coupler cups.  Quite different from many of the pressure-fit acoustic couplers that I've seen.   This one requires the use of on original-style Western Electric telephone...anything else won't latch into the coupler.  Fortunately, I've got a few of the old Western Electric telephone sets around here so I can test it out.     Not much information out there about this modem...when I get it working, I'll have to take some pix and maybe a video of it running with the terminal, and post a little video about it on YouTube. 

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.

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.

Along with the TTY, also came two TI Silent 700 780-series data terminals and an old TI calculator for the museum.

Anyway, I'm really happy to have finally after so many years to have got my hands on a trusty old Teletype ASR-33.

Happy Independence Day to all!

Rick Bensene
The Old Calculator Museum

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