RFI-EMI-GUY wrote:

There is a company that builds high voltage switchers for amateur radio
amplifiers, and there have been construction articles to build these.
(Check QEX magazine).

Regrettably the author of the key article, and owner of the company
"Watts Unlimited", died a few years ago.

The commercial unit followed some years after the QEX article. It
contained a number of important improvements but schematics were never
published. The big unanswered question is why that design had no voltage
feedback, and therefore had quite poor output regulation? (We can only
speculate that a feedback loop must surely have been tried, but proved
unworkable... and then wonder why that should be?)

An example application for the commercial unit:
http://www.gare.co.uk/k5and/8877.htm

Building from a surplus PC power supply would have a cost advantage.

These days, tube RF amplifiers only begin to show a clear advantage over
solid-state at 500-1000W RF output, ie 1-2kW DC input. That is way
beyond the capabilities of PC power supplies.

A small-scale project based on a PC supply would be a good way to begin
to understand the problems, at relatively little cost, but it would be
another big step to build (or modify) a much larger SMPS for a serious
tube amplifier.


--

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek

Ian White GM3SEK wrote:
RFI-EMI-GUY wrote:

There is a company that builds high voltage switchers for amateur
radio amplifiers, and there have been construction articles to build
these. (Check QEX magazine).

Regrettably the author of the key article, and owner of the company
"Watts Unlimited", died a few years ago.

The commercial unit followed some years after the QEX article. It
contained a number of important improvements but schematics were never
published. The big unanswered question is why that design had no voltage
feedback, and therefore had quite poor output regulation? (We can only
speculate that a feedback loop must surely have been tried, but proved
unworkable... and then wonder why that should be?)
(snip)

I worked on a 13.8 Volt SMPS made by TODD for Motorola as an OEM without
any documentation. There was a large stud mounted 13.8 Volt zener on the
output to clamp the voltage and some op amp circuitry to sense if the
output voltage fell below 13.8V it would start increasing the PWM to
charge the filter caps. This PS apparently never worked right because
the transformer leads were never soldered and then were plastered in
conformal coating.


--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P