[Amps] Series Capacitor Strings in HV Supplies

2 2 at vc.net
Thu Feb 27 01:04:28 EST 2003

>I have formulated a new theory which offers very convincing proof that the 
>traditional 'equalizing' resistors used with series-connected electrolytic 
>capacitor strings are NOT necessary. I realize that this contradicts the 
>prevailing wisdom, not to mention the design of hundreds of commercial amps 
>that have come and gone.

In days of yore, electrolytic capacitors were less than uniform, so V 
equalizers made sense.  Currently mfg electrolytics are quite uniform, so 
V-equalizers are probably of little or no value, except for discharging 
them after use.
>In lieu of just passing off what might be construed as idle speculation, I 
>have also done some meaningful practical work which supports my conclusion. 
>Specifically, I have been running 3 power supplies here over the last two 
>years with no resistors, one of them in my 'main' amplifier which is on the 
>air almost every day. To date, no sign of trouble. In addition, I have made 
>periodic spot checks of the voltage division between C's in each of the 
>supplies. Again, no unusual imbalances. 
>Now, I am preparing to make a public disclosure of my theory, which should 
>of interest to anyone building medium to high power amps. Stay tuned for 
>Meanwhile, I would like to hear any meaningful anecdotal data which supports 
>the old belief: that without balance resistors, an imbalance in the leakage 
>currents can lead to destruction of some C's. There are plenty of cases 
>the resistors themself failed, which guarantees a destructive imbalance 
>(that has happened to me). 

Good point.  High accuracy/high reliability  MOF resistors are much 
better than wirewound or carbon-comp resistors.  

>But has anyone ever seen or heard of a case where 
>'unequalized' capacitors blew? Unfortunately, few if any have ever dared to 
>even try it. The old myth was born many years ago and everyone is afraid to 
>question it. 
In the good old days, electrolytics were not uniform.

>Eric von Valtier K8LV

-  R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K, 

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