[GreenKeys] Model 19 Power Supplies

[Bruce Gentry]

A resistor to imitate the forward drop of a selenium rectifier will work 
well only with a fairly constant load. The punch magnets in a 19 
intermittently draw a good bit of current,  adjusting transformer taps 
(if there are any) or adding a bucking transformer to the circuit to 
reduce the voltage going into the rectifier  would be  far better. Be 
sure to use silicon diodes with at least a 1000 volt rating, the 
transient voltages in the punch magnet circuit can be quite high even 
with the snubber circuit. One great advantage of selenium rectifiers is 
their tolerence for transients and momentary overloads. They will endure 
a lot of abuse and survive.

      Bruce Gentry, KA2IVY


On 1/13/20 10:48 PM, w9ddd at tapr.org wrote:
> A long discussion about replacing selenium with silicon diodes here:
> https://antiqueradios.com/forums/viewtopic.php?t=305477
>
> My take away is you can approximate by putting a 100-200 ohm resistor 
> in series with the silicon.
>
> John, W9DDD
>
>
> On Jan 13, 2020, at 4:46 PM, E. <hanyou at xsmail.com 
> <mailto:hanyou at xsmail.com>> wrote:
>
>>
>> That�s one of the reasons why I have two power supplies on mine� one 
>> for the loop and the second for the DC punch side ;) .  Overkill, but 
>> better safe than sorry :) ~
>>
>>
>>> On Jan 13, 2020, at 4:39 pm, Jim Cooper <jim.w2jc at gmail.com 
>>> <mailto:jim.w2jc at gmail.com>> wrote:
>>>
>>> On 13 Jan 2020 at 15:44, Jim Haynes wrote:
>>>
>>>> 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.
>>>
>>> Keep in mind, also, that the reason for the
>>> regulation in the case of the Model 19 is
>>> that the punch solenoid takes a LOT of current
>>> in sharp, irregular bursts ... which could do lots
>>> of mess with the loop current if not regulated.
>>>
>>>
>>>
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