[GreenKeys] ASR33 Typing by itself at powerup

[Michael Katzmann]

Start with debugging the 'local mode'.
The selector magnet magnet is not energized (no 20mA current) (which is why
you are 'spacing' ... continuous nulls).
In local mode the connection is from the local loop current supply (see
schematic FS3) to the 'mode control' (see schematic FS4) to the Send
connections (schematic FS2) to the Receive (magnet driver) (see schematic
FS1) .
Note: A fault in either the keyboard, tape reader or answerback may give
the symptoms you see.  The answerback mechanism is (in my opinion)
particularly fragile and prone to cause this sort of problem.
If you have an external current loop and are spacing in 'line', I'd check
the signal through the receive circuit (FS1).

(https://www.soemtron.org/teletypemanuals.html)

good luck!

Michael

On Tue, Sep 7, 2021 at 9:33 PM <peter at mantos.com> wrote:

> I have a couple of ASR33 Teletypes and would like to get one working.
> When I turn on the primary machine to either line or local, it “types” what
> seems to be a null character repeatedly.
>
>
>
> As a bit of history, I had to do some work on my papertape power supply
> which I think I did successfully (although I accidentally touched something
> to it since and got a spark, so who knows?)
>
>
>
> That power supply repair seemed to work OK, but I couldn’t leave well
> enough alone and decided to do a little cleanup.  I ended up taking the
> spring(s) off the bottom of the keyboard, cleaned it, and replaced it.
>
>
>
> Since then, I have had the problem of it “typing” without any keyboard
> input when powered on.
>
>
>
> The reason I think that I have a NULL character is that if I turn on my
> papertape punch while this is happening, I get no holes in the tape except
> for the center sprocket holes.
>
>
>
> Any ideas?  I was thinking about transplanting the “other” keyboard, but
> from what I read, that’s just asking for trouble.
>
>
>
>
>
> Peter Mantos, MBA, MSCS, PMP, CSM
>
> Mantos I.T. Consulting, Inc.
>
> (505) 291-1047
>
> Not just “Know How”, but “Know Why”
>
>
> ______________________________________________________________
>
>

-- 
   |\      _,,,---,,_             Michael Katzmann
   /,`.-'`'    -.  ;-;;,_         NV3Z / VK2BEA / G4NYV
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