[Boatanchors] Dropping Resistor Question

[Mark K3MSB]

Power through each rectifier side will be E*I = (0.318*Vpp  * 0.318*Ipp)  =
0.101 Vpp*Ipp Watts

Power after each side will be (0.637*Vpp  * 0.637*Ipp)  = 0.405 Vpp*Ipp
Watts

The power in is each side ix 0.101 / 0.405 = 25% of that total.

Power dissipated by a resistor R in each side:

(0.318*Ipp  * 0.318*Ipp)R  = (0.101 *Ipp2)R  Watts

Power dissipated by a resistor R after each side:

(0.637*Ipp  * 0.637*Ipp)R  = (0.405 Ipp2)R  Watts

The power dissipation for a resistance R required in each side (0.101
*Ipp2)R / (0.405 Ipp2)R  Watts

which is (again) 25% of the total.

The GE and RCA data sheets state 175 mA max DC current.

The Tung-Sol data sheet that I was referring to states "Tube voltage drop
23V  at 175 mA per plate";  I think that really means Tube voltage drop 23V
per plate at 175 mA total output current after the legs are combined -- I
incorrectly interpreted what the data sheet was trying to convey.

So, if a Resistance R is placed after the rectifier output legs are
combined,  the power dissipation is P = IIR = 0.175*0.175*R.

So Bob, from the above calculations, I figure the power required in each
leg will be 0.25*P,  not 0.5*P.

73 Mark K3MSB







On Sat, Oct 7, 2017 at 7:17 AM, Rob Atkinson <ranchorobbo at gmail.com> wrote:

> I went through a period when I wanted to solid state all my power
> supplies and gradually learned that in many cases it was better to
> stick with the gas and vacuum rectifiers.  One time when solid state
> was needed was when bringing a supply up slowly with a variac.
> Another case was when the heat from the vacuum rectifier was cooking
> other parts too close to it.  Apart from those examples, the gear was
> made for the filament rectifiers and life is easier using them.  The
> filament winding on a multi-secondary transformer can handle it too,
> despite what many believe.  However, doing the circuit with a diode
> string and dropping resistor and in-rush thermistor can be a good
> learning experience.
>
> 73
> Rob
> K5UJ
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