On 2008-08-13, Ignoramus6985 wrote:
On 2008-08-13, BobH wrote:
dave wrote:

They probably do a couple of things. As Iggy mentioned, they will help
keep the HF out of the diodes. The other thing is that when diodes start
and stop conducting in a rectifier, they do so very abruptly, which
creates high frequency noise. This noise can cause interference problems
with nearby radio and TV sets (though nothing like the HF will) and it
can also shorten the life of the diodes. These caps will short that
noise to ground.

Bob, these are SCRs, for sure they stop conducting at zero crossing
only. As far as starting to conduct, are you positive that they do it
very abruptly? I thought that it was not the case, but maybe I am
wrong.

Nope -- they are *not* SCRs -- just plain rectifiers. No third
terminal for the gate input of an SCR -- and just the schematic symbol
for a plain (if heavy) diode.

Enjoy,
DoN.


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