[Amps] question for you experts...

[Vic K2VCO]

The reason that's usually given for this choke is as you say, in order to protect the 
operator in the event that the blocking capacitor breaks down. But I have also had the 
same thought that you have: the chokes used are rated at 300 ma and a big power supply 
with a hefty filter capacitor could give it a serious jolt that might not blow the fuse.

The other possibility is that it's to prevent DC buildup on the pi-network components 
which might precipitate an RF arc. Where would the DC come from? Maybe static electricity 
from the antenna. Maybe the charge on the blocking capacitor could induce a charge on the 
antenna if it's not grounded?

Food for thought. I agree the chokes are puny for safety devices!

On 3/27/2012 2:10 PM, Kathy Bookmiller wrote:
> I was doing some checking out everything on my amp. (NCL2000) and noticed that the
> 2.5mh choke that is after the loading capacitor in the amp. was open-connection/wire is
> gone. Looking at others amps., I see they all have them-it would be rfc3 in a SB200,
> 1.1mh., for example. Since they are in all amps, at least tube ones, what is it for? My
> guess it is to short out the HV if the coupling cap. shorted coming from the plates,
> but if I'm right, it doesn't seem heavy enough for a good power supply not to just burn
> it up and keep on putting the HV on the antenna/output. I think I can save the one in
> my amp. if I can get the paint off the wire by scrapping or chemicals and reconnect it,
> but by doing this, I'll eliminate one of the 4 sections on the choke, but doubt that
> change in value would be a big problem? Enlighten this poor QRPer, Kathy W2NK
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/