On Jul 26, 2004, at 1:27 AM, Steve Thompson wrote:
On Sunday 25 July 2004 11:49, R. Measures wrote:
If I wind the carrier power up and down, the screen current goes up
and down.
If I wind the power up and down at 2Hz the screen current goes up and
down at
2Hz and the meter needle will follow it. If I wind the carrier power
up and
down at 1kHz the screen current goes up and down at 1kHz but the
meter
needle
indicates steady 'average' current because it can't follow the
changes, not
because the current is actually constant. The regulation of the
voltage at
the audio frequency does matter. It's tricky winding the power
control
up and
down at audio frequencies manually, two tones does it more
effectively.
I agree, Steve. However, unregulated screen supplies have a
filter C
that is large enough to minimize 100Hz - 120Hz ripple, so that should
minimize V-out ripple (and IMD) when the load current changes at a
1000Hz rate.
Yes, it's possible to fool a two tone test with enough capacitance -
but in
order to approach the results you will get from an electronic
regulator, I
reckon you need a lot more capacitance than most would think to build
in,
maybe 500uF or more.
Steve -- For the current 8171 project, I'm going to start with 140µF on
the output side of a 1500V resonant-choke supply. If that does not get
the job done satisfactorily, I will go with something better.
end
Cheers,
Steve
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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