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julie_m · 15th Sep 2018, 4:53 am

So I made a SPICE deck:

Code:

* CAPACITIVE DROPPER FOR RECORD PLAYER VALVE HEATERS
* THE MAINS SUPPLY.  NOTE AMPLITUDE IS GIVEN AS PEAK
V1 1 0 SINE ( 0 340 50 )
* THE DROPPER CAPACITOR  (SEVERAL IN PARALLEL IF NEEDED)
C1 2 3 1u
C2 2 3 .47u
* R1 = SURGE LIMITER RESISTOR
R1 1 2 100
* R2 = BLEED RESISTOR
R2 2 3 470K
* V2 = MILLIAMMETER FOR MEASURING CURRENT
V2 3 4 DC 0
* R3 = THE VALVE HEATERS IN SERIES = 380 + 450 = 830Ω
R3 4 0 830

Then run

Code:

tran 1u 1
plot v(4) i(v2)*1000 v(3)-v(2) xlimit .5 .6

The [color=#red line represents the voltage across the valve heaters. The blue line is the current (in mA, because we are multiplying by 1000), and the oragge line is the voltage across the capacitor(s).

In other words, it seems to work just fine using a capacitance of 1.47µF (=1µF and 470nF in parallel) and a resistance of 100Ω in series with the valve heaters. The 470k resistor in parallel with the capacitors is there to provide a discharge path and so prevent a shock hazard from the plug pins after it is withdrawn from the wall. The capacitors should be rated for at least 400V and preferrably 630V. They will not need to be class X rated, due to the presence of a series resistance.

15th Sep 2018, 4:53 am	#8
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Garrard to BSR So I made a SPICE deck: Code: * CAPACITIVE DROPPER FOR RECORD PLAYER VALVE HEATERS * THE MAINS SUPPLY. NOTE AMPLITUDE IS GIVEN AS PEAK V1 1 0 SINE ( 0 340 50 ) * THE DROPPER CAPACITOR (SEVERAL IN PARALLEL IF NEEDED) C1 2 3 1u C2 2 3 .47u * R1 = SURGE LIMITER RESISTOR R1 1 2 100 * R2 = BLEED RESISTOR R2 2 3 470K * V2 = MILLIAMMETER FOR MEASURING CURRENT V2 3 4 DC 0 * R3 = THE VALVE HEATERS IN SERIES = 380 + 450 = 830Ω R3 4 0 830 Then run Code: tran 1u 1 plot v(4) i(v2)*1000 v(3)-v(2) xlimit .5 .6 The [color=#red line represents the voltage across the valve heaters. The blue line is the current (in mA, because we are multiplying by 1000), and the oragge line is the voltage across the capacitor(s). In other words, it seems to work just fine using a capacitance of 1.47µF (=1µF and 470nF in parallel) and a resistance of 100Ω in series with the valve heaters. The 470k resistor in parallel with the capacitors is there to provide a discharge path and so prevent a shock hazard from the plug pins after it is withdrawn from the wall. The capacitors should be rated for at least 400V and preferrably 630V. They will not need to be class X rated, due to the presence of a series resistance. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.