[GreenKeys] Run teletype model 15/19 keyboard and printer on different circuits?

[Harold Hallikainen]

I suspect this would work if you have at least 10 mA or so going through
the contacts. Less than that and you may get contact fritting.

It is common to just have the keyboard in series with the selector
magnets. I think there is always some contact arcing (though probably not
much at 5V).

As mentioned earlier, I put a snubber consisting of 100 ohms in series
with 470 nF was put across the keyboard contacts. This cleaned up the AFSK
generated by my TU-170.

Good luck!

Harold


On Tue, September 16, 2025 6:41 pm, Windows XD wrote:
> Dear all,
>
>
> I was working on the teletype when I had an idea. I have already picked
> up a solid state relay capable of switching faster than the 45.45 baud
> needed for the teletype for something else I'm working on with the
> teletype, and I was wondering if it would be possible to run the keyboard
> on a 5vdc circuit wired to said solid state relay and have the keyboard
> run on 5vdc and the selector magnets at 120vdc. I can't think of any
> obvious problems with running the keyboard at this lower voltage, but I'd
> like to be sure.
>
> I'm not sure I explained it super great so I've attached a schematic,
> although I'm not sure if it's any better than my explanation.
>
> P.S. My keyboard has arcing problems with the contacts, will this
> modification coincidentally also fix that?
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