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

[Teletypeparts]

Rob,

Mike is dead on with his diagnosis.  More detail than I have ever looked into.  Sometimes the twin wire contacts arent opening and closing fully when they should.  Its a swap sort of.  One opens and the other closes.  Sometimes you have to bend one of them ever so slightly to accomplish the required action.  

A good test is to be in Local mode and use the Bell feature.  You will know immediately what is happening.  

Mike, 

Did you enjoy your trip to Vermont?  I think you had good weather.

73,

Wayne
KB1FDW 



-----Original Message-----
From: Mike Douglas <deramp5113 at yahoo.com>
To: greenkeys <greenkeys at mailman.qth.net>
Sent: Sat, Oct 26, 2013 10:05 pm
Subject: Re: [GreenKeys] TeleType Model 33 Not Sending Some Control Characters Correctly




Robert,


Sorry it took so long for me to jump in - I've been out of pocket for a while.


If you have levers and contact wires on the left side of the keyboard that move with the control and shift keys, then yes, you have a parity keyboard. Also, your problem is clearly correlated to parity.



Note that every character you're having problems with has the parity bit set when control is not pressed. The control key is supposed to open the bit 7 path to make it a zero and then invert bit 8, the parity bit. It sounds like the contact wires on the left side may not be arranged exactly right in the plastic sliders and somehow the parity bit is ending up in bit 7. Can you get a really clear close-up photo of the left side contact wires for me? Can you tell me what is received for Bit 8 when you press a C and a Ctrl-C, for example?


Mike




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20131027/1ffd9896/attachment.html>