[GreenKeys] Teletype Corp. machine with a tube (was acrylic case)

[Duncan Brown]

Nick,

Teletype Corp did make a machine with an electron tube in it: the Model 
31 (AKA TT-30/AGA-1) that ran on 28VDC. A 35L6GT was used to switch a 
resistor into the motor circuit of the series governed DC motor for 
speed control. It was a KTP machine that was designed for use with 
RTTY/RATT. They were apparently afraid the normal open contacts in the 
speed control would produce too much RFI.  Although running on 28VDC, 
the 35L6GT apparently had enough gain with 28 VDC on the filaments and 
would probably last a bit longer.

The first time I powered up the Museum's unit, it seemed to run OK for a 
few seconds, but then it slowed down. I quickly killed the power and 
checked  the unit for something binding or a bad bearing. Everything 
seemed OK, so I powered it up and it did the same thing: slowed down 
after a few seconds. Then it ran fine and I suddenly realized that you 
had to wait for the tube to warm-up before the speed control took effect!

There is also a 250VDC generator connected to the TTY's motor to provide 
voltage for the loop and the FSK converter. So the TT-30, besides being 
the only TTY with a tube, is also the only  TTY with a dynamotor!

Have fun,

Duncan
K2OEQ

On 2/1/2019 20:29, Nick wrote:
>
> And the vacuum tube you can see on the lower right side above the 
> switch inside the case is just a little steampunk add-on. The tub 
> actually works, it is a Dekatron counting tub, spinning around to an 
> adjustable speed. At our event last weekend, I pulled somebody's leg 
> and said: "this is a super rare tube driven teletype machine, probably 
> the only one on the planet" - but the guy figured it out pretty 
> quickly and we both laughed.
>
> Enjoy the pics - any improvement ideas are always welcome.
>
> 73
>
> Nick  -  N0NCQ
>

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