Javier Albinarrate - LU8AJA

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Teleprinter Siemens T100a


Note: A lot has popped up from this project, and the article is now way outdated. Check this article too regaring the rewrite of the HeavyMetal software. As soon as possible I will give a huge update to this article.


I have just picked up an ancient mechanical teletype. It is a Siemens "Blattschreiber" T100a from about 1960.
This 32Kg beauty is in an overall good status, just a missing key, and with lots of dirt.
After a careful inspection I powered it on, and it went on without smoke (always a good sign Wink).
The electric motor works well, all gears move without problems, the paper tape writer makes holes, and everything seems to be fine.
So far I was only able to get lots of noise out of it, still not a single character was printed because it is not easy to find detailed technical information on these, plus I have no clue of what are some keys for, and I still need to build a current source and RS232 interface for interfacing it to a PC.

My next steps will be:

  1. Manual available here: http://www.vmarsmanuals.co.uk/new/t100fullmanual.pdf
  2. Understand how it operates, because it is rather messy
    • The transmitter consists of a Keyboard and a paper tape reader, information generated by these is sent to the ADo8 pins (yet to confirm)
    • The receiver consists of a printer and a paper tape puncher, which receive information coming from the ADo8 pins (yet to confirm)
    • Transmitter and receiver are not connected internally, thus if you try to operate the teletype without connecting them and/or without a current source, you'll only get noise.
  3. Mild cleanup, vacuum cleaner, etc
  4. Build a current source
    • There are many designs out there and they all consist of an isolation transformer of rather high voltage (80 to 130 volts), a diodes bridge and capacitor to rectify and filter it to DC, and a power resistor of several KOhm to limit the current to the one the teletype is designed for, typically 40 to 60mA.
    • I already ordered an isolation transformer, once I get this to work I will post the exact setup I used
  5. Connect the loop current supply to pins 1 and 4 of the ADo8 connector and jumper pins 2 and 3.
    • The jumper connects the transmitter and receiver together in loop so the printer will print what the keyboard types.
    • Thanks for the help to Henning Treumann (DF3OE) and Nico (OZ1BMC) from the GreenKeys list
    • Teletype plug
  6. Build a USB controller with a PIC, for which I have extensive experience (and I have a laptop without a COM port, so no RS232)

Siemens 100A

View with front cover closed

Siemens 100A

View with front cover open

Video from a similar/identical teletype (not mine)

 Related links

Last Updated on Sunday, 21 November 2010 19:25  

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