[GreenKeys] Model 14 keyboard adjustment

[David V. Corbin]

Yup, and that makes sense for circuits of 59 years ago. Now there are semiconductor devices that with 2 resistors to establish the current will regulate the output to the specific amperage. Measured (25 ft of cable into my ASR-33) rise times were fast enough that they were not measurable on the cheap scope I have there.

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________________________________
From: Jim Cooper <jim.w2jc at gmail.com>
Sent: Sunday, August 6, 2023 12:57:30 PM
To: David V. Corbin <david.corbin at dynconcepts.com>; greenkeys at mailman.qth.net <greenkeys at mailman.qth.net>
Subject: Re: [GreenKeys] Model 14 keyboard adjustment

On 6 Aug 2023 at 13:37, David V. Corbin wrote:

> This is why I use programmable
> current supplies rather than supplies
> where one sets the voltage.

Remember, you are dealing with mechanical
equipment and selector magnet magnetism
from the 1940s ...  just a simple  V --> R + L
series circuit where the important parameters are
60 mA of current and SHORT rise time based
on  L / R  ...

The L is fixed (selector magnet) so for shorter
rise time you need larger R in the series circuit;
a larger R means you need a larger V to get the
desired current.

THAT is why the old loop circuits were always
simply 100+ vDC with about 5k ohms.

w2jc



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