[Amps] .01uf caps across diodes ?

[MU 4CX250B]

Hi Tim,
I’ve followed this debate for years and frankly I don’t think adding
.01uF caps across each diode in a diode string makes much difference
one way or the other. It’s true that there will be some suppression of
fast current and voltage transients, but these aren’t likely to cause
damage to modern components. To me the downside of the practice is
that adding 0.01uF caps results in additional opportunities for
capacitor failures, loose solder connections, unsightly wiring, and a
bunch of extra components that provide minimal benefits. I’m inclined
to leave them out. (BTW, one commenter suggested that sharp voltage or
current spikes wouldn’t make it through the filter capacitors. That’s
untrue because the filter caps have a self inductance that keeps them
from filtering spikes with high frequency components. )
73,
Jim W8ZR

Sent from my iPhone

> On Dec 11, 2022, at 7:03 PM, Tim Duffy <k3lr at k3lr.com> wrote:
>
> W8ZR Jim
>
> Can you give advice on this topic?
>
> 73
> Tim K3LR
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of jim.thom
> jim.thom at telus.net
> Sent: Tuesday, November 29, 2022 2:28 PM
> To: amps at contesting.com
> Subject: [Amps] .01uf caps across diodes ?
>
> What's the consensus on wiring .01uf disc caps across diodes in a HV supply
> ?
> W8JI sez they are required, and used in ameritron amps....and used to
> eliminate switching transients.
>
> Some say the caps are required to meet emc specs on commercial gear.
>
> I can't see how anything can get past the HV fitter caps.
>
> KM1H also uses caps across diodes.  He also used another method, with a
> .01uf cap across an entire series string of diodes, like a .01uf @ 5 kv
> type.
>
> Orr's books recommend caps across diodes... to eliminate noise on TX on
> ssb. .
>
> Are they required...or not ?
>
> Jim  VE7RF
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