[Amps] Small transformer evaluation

[Vic K2VCO]

It's going to feed a transistor regulator. I'm sure it will be a capacitor filter because 
of the voltage.

On 9/1/2012 1:55 PM, Bill, W6WRT wrote:
> ORIGINAL MESSAGE:
> On Sat, 01 Sep 2012 13:37:10 -0700, Vic wrote:
>
>> Some of you will remember that I was wondering about utilizing a small Philco power
>> transformer (model 45-7011-7) for a screen supply. It puts out 380-0-380 vac plus 5 and 6
>> v for filaments. I have hooked it up jn a full-wave ct circuit feeding a choke-input
>> filter and 20 uf capacitor. It is feeding a 4300 ohm 50w resistor for a load.
>
> REPLY:
> You should not use a choke input filter for a screen supply except for constant
> carrier modes such as FM or RTTY. When the screen current varies as with SSB and
> CW, the varying current through the choke will cause voltage spikes and slumps.
> You can easily see this with an oscilloscope. The screen voltage should always
> be constant.
>
> A simple capacitor-only filter is best. And it will solve your low-voltage
> issue.
>
> 73, Bill W6WRT
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/