[HomeBrew] Dual output power supply?

[N2EY@aol.com]

In a message dated 2/14/04 1:33:28 PM Eastern Standard Time, 
n6kyr@netzero.net writes:


> I need help for a power supply I'd like to build. The output I'd like to 
> have will be around 400-600 VDC (about 90-100 mA) for the plate supply and 
> 200-250 VDC (30 mA) for the screen supply. I found a 600 VCT, 250 mA xfmr from 
> Hammond that I have on hand. The prospective circuit would be to use a full 
> wave bridge the two outer windings and run it through a pi networked choke/2-cap 
> filter. The center tap will not be grounded but instead, run through another 
> choke and filter cap. I saw a similar circuit on building up a vintage 
> transmitter. Does anyone have any design considerations or comments about doing 
> this type of circuit? 
> 
> 

What you describe is known as the "economy" power supply. Goes back more than 
50 years. 

The main concern in your application is the output voltages. If the 
transformer delivers 600 VAC to the bridge rectifier, the output voltages will be as 
high as 840 VDC on the high tap and 420 VDC on the low tap if a capacitor input 
filter is used (you get the peak voltage if the input capacitor is big enough) 
. If you use choke-input filters and the input choke has at least critical 
inductance, the output voltages will be as high as 540 VDC and 270 VDC. 

So you can see that the filter design requires a bit of consideration...

What sort of rectifiers will be used, and is the load steady or varying?

Will the transformer be used for heater windings as well, or just B+?

73 de Jim, N2EY

(who just brought a nice pair of 866As out of remote storage...)


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