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[AMPS] Additional Info Voltage Doubler/Filter Capacitance

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Subject: [AMPS] Additional Info Voltage Doubler/Filter Capacitance
From: (2)
Date: Fri, 21 Sep 2001 08:23:52 -0700
>>    Thanks for the info so far. Additional info is as follows: The
>>    transformer was designed to be used with a doubling rectifier. The
>>    secondary is 900 volts +or- 5%. The secondary resistance is 16
>>    Ohms. (primary will be wired for 240V).
>Ouch Kurt!! That is very high resistance, because the secondary 
>ESR (equivalent series resistance) will be substantially higher than 
>the secondary dc resistance. The actual resistance seen by the 
>rectifiers and capacitors will include 16 ohms plus core losses and 
>primary/power mains resistances!
>You want to use a conventional (full-wave) doubler, and not a 
>cascade (half-wave) doubler. Cascade multipliers have less 
>regulation and more ripple, and are mostly used where one side of 
>the source is grounded or you need high multiplications.
>Doublers are actually just as good as bridge rectifiers IF the 
>transformer is the same size and fully optimized. It does not sound 
>like your transformer is sized for four 572B's at all.  
>Assuming you have 2500 ohms of DC load resistance from the 
>tubes (1600 watts tube input power), and 30 ohms of ESR (which 
>is reasonable for a 16 ohm DC resistance secondary when used on 
>a very stiff power line) and 2 ohms of secondary ESR caused by 
>the capacitors and power line resistance, around 80-100 
>microfarads will be optimum.
//   The Heath SB-220's HV filter is 50uF per half of the FWD, or 25uF 
total.  The 220 does c. 2800v @ 800mA-peak with no apparent problem. 

>The voltage will be 2500 volts no load and almost certainly well 
>under 2100 volts full load. Any amount of capacitance above 80-100 
>uF (for each half of the series string) will NOT improve things.

-  R. L. Measures, 805.386.3734, AG6K,  

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