Image Map Image Map
Page 1 of 2 12 LastLast
Results 1 to 10 of 13

Thread: ASR33 - Starting the tape reade in line mode

  1. #1

    Default ASR33 - Starting the tape reade in line mode

    Hi everybody!

    I would like to use the tape reader of my Teleprint 390 (=ASR 33) Teletype.

    It works fine in local mode. But when I am in line mode, the reader will not start by shifting the "start" lever forward.

    Anybody familiar with that behaviour?

    Regards
    Stephan

  2. #2

    Default

    Does it start if, when in AUTO mode, you send XON from the computer?
    - Doug

  3. #3

    Default

    Quote Originally Posted by durgadas311 View Post
    Does it start if, when in AUTO mode, you send XON from the computer?
    Thanks for your reply! No unfortunately not. I tried so send all possible CTRL Codes, including CTRL-S & T with no success....

    What does AUTO mode mean?

  4. #4

    Default

    As I recall, the tape reader switch had 3 positions - stop, auto, start. I think Stop and Auto were static positions, while start was momentary (spring loaded return to "auto"). In auto mode, the teletype would respond to Ctrl-S and Ctrl-Q in order to stop and start (respectively) the tape. (this may have been the origins of the XON/XOFF protocol used to do software flow control on serial ports - not sure which came first).

    If Ctrl-Q (XON) does not start the tape with the lever positioned on "auto", and manually pushing the lever to "start" and releasing does not start the tape, it sounds like there is some basic failure of the tape read mechanism. But again, I'm getting out of my depth. Is there any sort of mechanical activity when you push to "start"? Or is it as if the mechanism is disconnected? You say that it works in local mode, which is odd because the mechanics are the same. I wondered if there was some hardware handshake going on with your unit, whereby the computer needs to raise CTS or some such thing in order to allow the tape to run. I'm not sure if anyone ever rigged up a TTY to do that, I never saw it but really did not work with many situations. Are you able to communicate from the keyboard to your computer, and computer to print/punch unit?
    - Doug

  5. #5

    Default

    Quote Originally Posted by durgadas311 View Post
    As I recall, the tape reader switch had 3 positions - stop, auto, start.
    Thanks very much for your comment. I tried it out again with no success....

    My machine has only "START", "STOP" and "FREE" positions - no idea what "free" means.
    My switch will rest in all three positions.

    In none of the three switch settings, the reader will start on CTRL-S or -Q issued from the terminal which I have connected to the machine (in line mode).

    I have hooked the machine up to an MS DOS PC using a 20mA current loop interface. I can print and punch, and read the tapes back in local mode. I can see the characters on the PC-Terminal (KERMIT) when I press keys on the ASR 33 keyboard.

    There are two pin at the data cable from the machine where I do not know iths purpose. They lead to a solenoid of a reed contact relais... I have trouble to understand its function. I do not have a schematic of the "Teleprint" electronics boards unfortunately which are not the same as in the original Teletype 33.

    I am sure it works as the previous owner told me the reader was used to read programs to a SIEMENS 300 computer (back in the 70s)

    Regards,
    Stephan
    Attached Images Attached Images

  6. #6

    Default

    "free" means that the tape feed sprocket is "free", and the tape can be manually pulled back/forward to position it.

    The looks like a standard KSR/ASR-33 frame, re-packaged for another purpose. Can't tell for sure whether it is KSR (no XON/XOFF) or ASR.

    Let me ask a basic question. When in "line" mode and you push the tape reader lever to "start", is there a position slightly past "start" that is spring-loaded? (picture seems to indicate no space for that) Typically, the "start" function is a momentary switch, but there were many models and I don't remember all the ones I worked with.

    Also, when you say the reader doesn't work, is it that the characters on the tape do not print? or that the tape doesn't advance at all? When in "line" mode, characters you type/read will only appear on the paper if the remote machine (computer) "echoes" them back. In "local" mode, the tty output is looped back to input, so everything you type/read is implicitly echoed.
    - Doug

  7. #7

    Default

    Quote Originally Posted by durgadas311 View Post
    "free" means that the tape feed sprocket is "free", and the tape can be manually pulled back/forward to position it.
    Yes you are right about the "free" position, great, thanks for the information !

    I have no idea if the machine is ASR or KSR... I have no documentation, but it looks like this machine here http://www.computinghistory.org.uk/n...ers-Preserved/

    There is no position past the start switch.

    In "LINE MODE", the reader does not advance the paper strip. When the reader is in start position with a paper tape loaded, it starts immediately reading and printing when I turn the mode switch from "LINE" to "LOCAL".

  8. #8

    Default

    That is starting to sound like some sort of remote control to prevent the tape reader from going off before the other end was ready. Maybe that relay you saw is connected to enabling/starting the tape reader. You'd either have to experiment with it or remove all the covers and examine the reader mechanism. However, I'm not sure where the electrical-to-mechanical link might be - it could be nowhere near the reader itself (as I recall, there are linkage arms all over the place there, extending across the keyboard and even back into the print unit).
    - Doug

  9. #9

    Default

    Sounds like it might have a reader-run circuit installed. This was somewhat common for DEC machines. You'll probably find a card with a relay on it if so.

  10. #10
    Join Date
    Oct 2008
    Location
    Kamloops, BC, Canada
    Posts
    5,598
    Blog Entries
    43

    Default

    My teletype machine has the Automatic Reader and thus four switch positions in this order:

    -Manual start
    -Auto
    -Manual Stop
    -Free

    You already know what "Free" does and "Manual Start" and "Manual Stop" are momentary and return to "Auto" when released.

    The Automatic Reader Run mechanics are two momentary switches inside the teletype.
    = Excellent space heater

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •