[AMRadio] High Voltage Power Supplies

W5OMR/Geoff w5omr at satx.rr.com
Sun Oct 30 10:15:00 EST 2005

Ed Swynar wrote:

>Hi Jim,
>Many thanks for all the info!
>Well, mine is the "classic" late 70's era string of 7 diodes per leg, each
>paralleled with a resistor / disk capacitor combo. The transformer is,
>indeed, centre-tapped, & the design is full-wave rectification, the output
>of which goes directly to a series of "parallel resistor-equalized"
>high-voltage electrolytics.
>The transformer itself is a classic --- an old Fred Hammond job, with a cast
>iron(!) frame! The thing weighs-in at a "mere" 90 pounds! I got it surplus
>NOS from an old surplus house in Montreal some 30 years ago now...
>I took a suggestion of Bry's, Jiim, & placed an RCA plug-in type surge /
>transient suppressor that I happened to have available between the p.s. &
>the AC outlet --- that is one thing that I'd never done before. If / when
>the supply fails again in future, I'll most likely "upgrade" the silicone
>string with some of the newer, more robust chunks of silicone that were
>simply unavailable 30-odd years ago...

Simply because I like tubes, I'll make this suggestion...

3B28's are -much- more forgiving as far as transients.  866's are too, 
but they tend to generate some noise in the reciever.  I've never 
noticed it, but then again I mostly operate 40 and 75m and any 
background noise would cover up the little noise that might be generated 
by the mercury vapor rectifiers.

I'm fixing to start on a choke input power supply here, that will 
incorporate a pair of 872A's, a 3.2kV (@ 2.5kVA) plate transformer, a 
couple of 4henry chokes @ 500mA and some 18uf of capacitance, @ 4kVDC.  
I'll control the primary voltage of that transformer with a vari-ac.

73 = Best Regards,

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