[GreenKeys] TeleType Model 33 Not Sending Some Control Characters Correctly

[Robert Jarratt]

I have had two replies on this and finally got a chance to look at it today.
I was asked if I had moved the machine, while the answer is yes, the problem
had started before I moved it.

 

I have been looking at the manual and at my machine and I am slightly
confused. I believe I have a parity keyboard. The manual 574-121-100TC in
Fig. 10 shows a set of contact wires at the left and the right that are
operated by the CTRL key.

 

However, on my keyboard there are no contact wires on the right (as you look
from the front) operated by the CTRL key, nor is there room for any; it
doesn't look as if anything is missing or broken either. In fact if that was
the case then it would not work with any letter keys at all, but the reality
is that it works correctly for some keys but not all of them.

 

>From what I can see, the operation of the CTRL key is always the same. It
changes the contact wires on the left of the keyboard regardless of what
letter key I press at the same time, and on the right it has no effect at
all on the contact wires. So I don't get why sometimes it seems to work and
other times it doesn't.

 

Regards

 

Rob

 

From: Robert Jarratt [mailto:robert.jarratt at ntlworld.com] 
Sent: 21 October 2013 22:15
To: greenkeys at mailman.qth.net
Subject: TeleType Model 33 Not Sending Some Control Characters Correctly

 

My Model 33 had been working perfectly. But for some reason it has started
not to send some characters to the computer correctly.

 

For some reason CTRL-C (ASCII 3) is sent as "C" (ASCII 43 in hex). For what
I need it for this is disastrous because it is the character I need to send
to start the login sequence on the simulated computer that I need it to log
in to. I have checked all the CTRL keys, the ones that don't work are
CTRL-C, CTRL-E, CTRL-F, CTRL-I, CTRL-J, CTRL-L, CTRL-O, CTRL-Q,  CTRL-R,
CTRL-T, CTRL-W, CTRL-X, in each case hex 40 is added (ie bit 7 is set). It
does not even seem to be a parity issue because contiguous characters are
sent incorrectly.

 

Ordinary letters are sent correctly.

 

Any ideas where to start looking?

 

Regards

 

Rob

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