[NJARC] BC-348Q Power Questions - Sanity Check

[Scott Roberts]

I forgot to ask in my last posting- I am using two
electrolytics between B+ and B-, on either side of the
filter. They are 47/450 & 44/450(pair of 22/450) which
kick the power up by 80VDC. If I were to change it to
a 22/450 on either side of the filter instead, would
the effect still be the same, but the voltage increase
less?

Scott



--- Scott Roberts <ng19delta at yahoo.com> wrote:

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Ok. I will be the first to admit I know very little
> about electricity. Other than the quick course I had
> in A&P mechanics, I have had no formal training. And
> that was over a year ago... I try to look up stuff
> first, and apply the formulas I half remember, but I
> am still struggling. Once the discussion gets
> electro-technical, I  struggle a little. I will be
> getting better at this, but it will take a while.
> 
> I have my power supply for the BC-348 together.
> First
> the good news- the 24VAC supply for the heaters is
> putting out the right voltage. 
> 
> The main transformer is putting out about 500VAC,
> with
> 250 coming out the tap. The two 500V lines are
> passed
> through a pair of 1N4007 diodes for rectification.
> At
> this point, I get around 250VDC The B+ line then
> connects to a 47/450 electrolytic(to B-), then a
> filter, then a pair of 22/450 Electrolytics(in
> parallel with each other for 44/450)(to B-) then
> out.
> At this point, I am getting 330VDC.
> 
> So I tried clipping in a bleed resistor between B+
> and
> B-.  I tried a 125 ohm resistor, and power dropped
> below 200VDC. So I tried a smaller resistor, and the
> voltage dropped further! This surprised me, but
> thinking it over, it is starting to make some sense.
> The less resistance, the more return, so lower
> voltage. I finally got the voltage to the right
> spot-
> by clipping 5-500ohm resistors in series, for
> 2500ohms
> total. The resistors I am using for this test are
> marked "Dale RS-10 500ohm Mexico" and are about
> 5/16"
> dia. by two inches. The specifications I found
> online
> state:  RS-10 
>     * Wirewound Resistor
>     * Series:RS
>     * Resistance:500 ohm
>     * Resistance Tolerance:+/- 1 %
>     * Power Rating:10W
>     * Resistor Element Material:Ceramic
>     * Temperature Coefficient:+/-90 ppm
>     * Leaded Process Compatible:No
>     
> Would these resistors, placed in series and parallel
> to the electrolytics, be acceptable to drop the
> voltage during use? I imagine a 10W wirewound would
> be
> adequate...
> 
> Scott
> 
> 
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