[GreenKeys] Model 28 Typing Unit activated immediately at power-up. What's stuck?

[steve bennett]

 Tim,
  I think that is what is known as "running open".When you energize the DC current loop it should stop doing that.
You need to do your homework and find out how many mA of DC current it takes.
The machine expects mark and space signals.Current flow = Mark.Absence of current = Space.
With no signal present the machine thinks it is getting a continuous string of spaces.
-Steve

    On Thursday, August 26, 2021, 12:23:13 PM EDT, Tim Griffin <tim.griffin at enwood.ca> wrote:  
 
 Hi all;
I have just joined Green Keys because of my acquisition of a Teletype Model 28 KSR, that appears complete and semi-operational, and am seeking a little diagnostic expertise before I start hunting too much. I have downloaded many manuals and service bulletins for the unit, and am definitely intimated by the myriad adjustment procedures that I'm not keen to touch anything until I know where I'm headed. 
I've posted a short video that illustrates what the machine is doing as soon as it's powered up. 
https://www.dropbox.com/s/gda9n2j3gxh0tl5/Teletype.MOV?dl=0

It begins "printing", and while the ribbon advances, there is no print head advancement, and the Keyboard Lock key jumps up and down at each cycle. The teletype is not connected to any signal source, so this behaviour suggests something stuck, worn out, worn down... I'm not sure what. 
Can anyone give me a general sense of things to consider at this initial stage? 
As a little background, I'm a collector of telephony equipment here in Canada (Step-by-Step, switchboards, intercoms, telephones etc.) as well as some vintage computers, and IBM Selectric typewriters. All of these things are challenging to master, but I'm seeing this Model 28 as perhaps the biggest challenge yet! The unit I've acquired was once in service in the Canadian National (Railway) office in Chicoutimi, Québec, in use up until about 1977. (It's equipped with a 7.5" sprocket-feed platen (rather than 8.5"), so my guess is that it was used for printing rail tickets, forms etc. but that means I'm also on the hunt for either 7.5" sprocket paper (none found yet anywhere), or an 8.5" sprocket-feed platen that would allow me to use regular bi-fold computer paper.)
But, before it prints anything for real, any pointers on its current behaviour would be most welcome as a start!
Tim GriffinOttawa, Canada








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