[GreenKeys] Model 19 Power Supplies

[Jim Haynes]

The one with thyratrons was used in the military where the power frequency
was not stable.  Otherwise Teletype preferred to use constant-voltage
transformers, but those are frequency sensitive.

I've seen a power supply with the Western Electric name and it used
magnetic amplifier regulation, with a couple of VR tubes as the voltage
reference.

I have a 19 used by Western Union and they put in their own power supply,
one without a constant-voltage transformer.

If I had one with selenium rectifiers I would probably replace them with
silicon.  The output voltage would be higher, but shouldn't cause any
problem.  If you're using that rectifier for loop power as well as for
running the punch you'd need to adjust the loop current because of the
higher voltage.

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