[GreenKeys] Power supply recommendation

[David V. Corbin]

I am on my phone right now, but when I get back to my desk I will post what I built last year. It can easily be changed from 20mA to 60mA and is a fixed current supply (along with detector so it can be used for either)

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From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net> on behalf of Ralph Mowery <rmowery42 at charter.net>
Sent: Thursday, July 27, 2023 3:12:03 PM
To: greenkeys at mailman.qth.net <greenkeys at mailman.qth.net>
Subject: Re: [GreenKeys] Power supply recommendation


Are you up to building simple circuits ?



For a simple one you can get a wall wart of around 12 to 20 volts at an amp and a half or so, a up converter circuit board off ebay  for around $ 5 a 10 to 20 watt resistor of around 1000 to 2000 ohms.  Drive the up converter with the wall wart, put the resistor in series  with the printer magnets and adjust the voltage to get the 60 ma for the loop.  The voltage is not critical at all from around 70 to 200 volts.  It is the current that maters it needs to be close to 60 ma…  Do not go over that or possible damage to the magnet windings may happen.



To operate the tape punch it needs around 100 volts at 1 amp as I recall.  Just to use the printer and keyboard all you need is the 60 ma loop.



As you can see from the above the voltage is not critical, it is the current..  The magnets will pull in at a much lower voltage, however due to the inductance of the magnets  , the printer will not work very well with voltages less than 50 volts and the higher the voltage the better the printer will work.



Ralph ku4pt







From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Windows XD
Sent: Tuesday, July 25, 2023 1:10 AM
To: greenkeys at mailman.qth.net
Subject: [GreenKeys] Power supply recommendation



I’m very new to teletypes, and I want to get my model 19 running. I’ve done the hard part of cleaning, but now I need a 120VDC 60MA power supply. Is there any that you would recommend?
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