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

[Mike Douglas]

Rob, 

Your left contacts look correct in the photos. The contact pair actuated by the control key (call them L and R for left and right):

Ctrl NOT pressed: L closed, R open
Ctrl pressed: L open, R closed

First step, I'd clean out the fibers I see in the photos, then clean the contact wires and the common bars where they touch each other with contact cleaner (do this for all contact points on both sides of the keyboard).

Mike

> On Oct 27, 2013, at 1:46 PM, "Robert Jarratt" <robert.jarratt at ntlworld.com> wrote:
> 
> Good idea! Here are the codes that got punched
>  
>      A 10000011
> CTRL-A 10000001
>      C 11000011
> CTRL-C 11000011
>  
> Seems to behave as if parity is stuck at 1 and bit 7 is being set as if were the parity bit.
>  
> Regards
>  
> Rob
>  
>  
> From: Mike Douglas [mailto:deramp5113 at yahoo.com] 
> Sent: 27 October 2013 18:28
> To: Robert Jarratt
> Cc: Teletypeparts; <greenkeys at mailman.qth.net>
> Subject: Re: [GreenKeys] TeleType Model 33 Not Sending Some Control Characters Correctly
>  
> Rob,
>  
> Run in local mode, turn on the punch and type two A's, two Ctrl-A's, two C's and two Ctrl-C'sTurn on your punch. Let me see the tape in a photo.
>  
> I still hope to get to my Teletype this afternoon to tell you exactly what the left side contacts should be doing when Ctrl is pressed.
>  
> Mike
> 
> On Oct 27, 2013, at 1:18 PM, "Robert Jarratt" <robert.jarratt at ntlworld.com> wrote:
> 
> CTRL-G works as expected in LOCAL mode, ringing the bell. But if I press CTRL-C it prints a C. It does seem as if bits 7 and 8 are swapped, but if that were true it would never have worked, and yet previously it has worked fine.
>  
> The only thing that comes to mind now is that I did take the typing unit out not so long ago, could I get this problem if I didn’t put it back properly?
>  
> Regards
>  
> Rob
>  
> From: Teletypeparts [mailto:teletypeparts at aol.com] 
> Sent: 27 October 2013 17:40
> To: deramp5113 at yahoo.com; greenkeys at mailman.qth.net; robert.jarratt at ntlworld.com
> Subject: Re: [GreenKeys] TeleType Model 33 Not Sending Some Control Characters Correctly
>  
> 
> 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
> 
>  
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