[GreenKeys] 33 ASR Troubleshooting - keyboard works in local mode but not line, etc.

[Thomas Moss]

Please disregard previous message, I hit send by mistake.
It should have read:

Hi All,

I've recently acquired a couple of 33 ASR's that I'm in the process of
restoring, and so far have fixed an issue they both had that stopped
carriage return or linefeed from working.

Now, both units appear to be working fine in Local mode, but when I
switch them into Line mode with one of Mike Douglas's Current Loop to
RS232 adaptors* attached, I get the following:

TTY 1: Can receive characters fine, but cannot send.
I hooked up the output side of the RS-232 adaptor to an oscilloscope but
did not see any sign of a signal.

TTY 2: Remains open even with adaptor connected.
I tried connecting a 9v battery across pins 7 and 8 of P2 on the UCC6,
which stops it from running open.

I followed some of the advice on theretrowagon.com** under "Testing
Running Open", I wasn't sure exactly which steps applied though as it
does run closed in Local mode.

Some notes:
-Swapping SMD cards across units doesn't appear to change anything, and
   the large flat green resistor in the UCC6 appears fine.
-Fuses are all good.
-They appear to be configured for full duplex
-There's a extra card inside each unit marked "TELETYPE CONTROL",
   that doesn't appear to be part of the standard UCC6, that connects
   between some of the internal wiring, and includes a knob marked "AUTO"
   and "ON". The knob is normally in the "AUTO" position, with the "ON"
   position being momentary. It doesn't appear to do anything in Local
   mode, but in Line mode the knob must be turned to "ON" for the motor
   to activate. After a minute or so the motor turns itself off,
   regardless of whether or not it's receiving data.
-There is a unit marked
   "MASTER BRD. F/TELETYPE OLIVETTI" inside the pedestal that has
   connections for "READER", "TELETYPE NO 2.", "SCALER", and "SOLEDNOID
   DECK".

I'm pretty new to this as it's my first time working on Teletypes, and
I've only had these a few days. Any pointers as to what to look for
would be greatly appreciated. I wouldn't be surprised if the
non-standard features have something to do with it, and would be
interested if anyone knows what the Olivetti parts are for.

*https://deramp.com/downloads/teletype/TTY-RS232%20Manual.pdf
**https://wiki.theretrowagon.com/wiki/Teletype_Model_33#Testing_running_open


Regards,
-Tom

mosst at sdf.org
SDF Public Access UNIX System - https://sdf.org