[GreenKeys] Siemens T 100 garbles when hot

[Duncan Brown]

The AWA Museum has a RCA branded Siemens T 100 Telex machine with a 
Telefonbau U. Normalzeit interface/loop supply box.  When we first got 
it, I lubed it and it seemed to run fine, but then it went into 
storage.  We have recently opened a larger TTY display and it is part of 
it.

We recently had about 70 3rd graders come through the Museum and I 
entertained them by having them type their name on the T 100 and receive 
their name "in code" on a piece of tape that they could take home. This 
went over great and kids came back to punch out their siblings, parents 
& pets names!

But after about an hour, the machine started to garble by occasionally 
adding extra bits.  The kids didn't notice it but I was concerned. After 
the unit cooled down it was OK. I have seen other machines that had not 
been run for years type poorly until they warmed up the old grease, but 
I've never seen one that printed poorly after running for an hour.

Assuming that this is an electrical problem, I pulled a wire off the 
selector magnet today to measure the open circuit loop voltage and it is 
only about 20V!!  Is this normal for a T 100?   shouldn't it be the 
typical 120V?  Loop current is the proper 40 ma. (voltage & current were 
about the same whether printing properly or not)

Does anyone have a schematic for the Telefonbau U. Normalzeit 514 53/12 
Telex box that contains the loop supply?

Thanks,

Duncan Brown, K2OEQ
USASA  31J30

Antique Wireless Association Museum Asst. Curator, Commercial Equipment
(also Chief TTY operator & repairman)
http://www.antiquewireless.org/


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