The keyboard SHOULD be a short when idle. Perhaps one of the switch
contacts is bad. It also may appear to be an open circuit at low voltage
and current and do fine with high voltage and current (60 mA). The
keyboard should indeed be in series with the selector magnets.

Good luck!

Harold

On Wed, February 26, 2025 12:09 pm, steve bennett via GreenKeys wrote:
> GKs,
>
>  Greetings. John Lawson was kind enough to send me a keyboard for my model
> 15 and
> I am trying to figure out how to wire it.
> My machine is a RO and is not equipped with the electrical contacts for
> the keyboard.
>
> I thought it would just be wired in series with the printer but apparently
> I was wrong.
> The keyboard is an open circuit when in the idle state and when a key is
> pressed contacts in the
> mechanism close in sequence to produce the code.
> Exactly the opposite of what I was thinking it would do.
> If I wire the keyboard in parallel with the printer it will appear as a
> short circuit to the loop supply
> when contacts close so it would effectively shunt the selector magnets and
> short out the loop supply.
> (My loop is a Flesher TU170)
>
> That does not sound safe.
> Can someone explain how this is supposed to work? Do I need at add a
> current limiter to the keyboard or does
> it do it's own current limiting?
>
> And does polarity matter?
>
> Thanks,
> -Steve
>
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