----- Original Message -----
From: "Jim Thomson" <Jim.thom@telus.net>
To: <amps@contesting.com>
Sent: Tuesday, February 23, 2010 8:13 AM
Subject: [Amps] 120 hz hum
> Uhh....Im not complaining about the LK-500 regulation, simply stating a
> fact.
>
> Now if you want to look at the classic Alphas of the 7 series, Ameritron,
> Ten Tec, Heath, Dentron, Drake, Swan, etc, etc, you will find them in the
> 17-33uF range....duh.
>
> The latest series of some amps have more C as a result of capacitor
> technology, not engineering brilliance.
>
> Going back further to the 1963 NCL-2000 it is 10uF AS PER THE RCA specs
> for
> the 8122's. Static regulation at 0 to 2000W is 16%. Dynamic is much better
> for SSB.
>
> Carl
>
> ## well, I guess RCA got it wrong !
** RCA was more concerned about energy storage than ripple. They even
specify a 15 Ohm glitch resistor, the value of the screen electrolytic and
its glitch resistor. Burle hasnt bothered to change the specs either.
When I had to replace the 80uF filters in the 6M NCL-2000 I mounted 330uF
450V CDE snap ins on some perf board. Static regulation didnt improve that
much, the xfmr winding R must be rather high.
Carl
>
> ## yes, cap technology has really improved a whole bunch.
>
> ## A buddy of mine lucked out, and found some spanky new
> 450 V lytics.... 4800 uf [ four thousand, eight hundred].. EACH. ESR
> on them is
> .025 ohms [25 milli-ohms]
>
> ## Ripple current rating is 40A ! I checked both Hammond's and CD's
> engineering notes, and went through all the math's, and sure enough, with
> a simple
> C input filter, ripple current = 2.56 x DC plate current.
>
> ## Anybody who doubts the virtue of really high C filters, just try it.
> The PEP
> output on the wattmeter is WAY up. Ripple is almost zero. I'm 100%
> convinced IMD
> is down as well. For folks who play with ESSB, you can actually hear the
> difference
> between stock C value... and 2-6 X stock C value.
>
> ## step start procedure is much the same. The step start resistor value
> has to be
> reduced in value, and shorted out after a longer time period. This will
> eliminate the
> sec surge. Caps charged up to only 1/2 normal B+.. will only have 1/4
> of the energy.
> Joules = uf X [B+ squared] .../ 2 million. Caps charged up to
> 71% of normal B+
> only have 1/2 the energy. So you can see, to minimize the sec surge, you
> want to charge
> the caps up as high as you can.. just prior to shorting out the step start
> resistor.. which may
> be several seconds. A lower value R means less V drop across the same
> step start R, and
> higher B+..prior to shunting the R.
>
> ## they never can be fully charged with normal step start R... because
> the magnetizing current
> in the plate xfmr pri.. is always flowing through the step start R.
> Another method to step start
> is to use a small variac in the pri, and switch it out of the circuit
> completely, with a small relay.
> This method allows the caps to be charged up to 99% of normal B+... and
> no sec surge.[and
> no pri surge either].
>
> later..... Jim VE7RF
>
>
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