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Re: [Amps] GS35b FWB issue

Subject: Re: [Amps] GS35b FWB issue
From: Ian White GM3SEK <>
Reply-to: Ian White GM3SEK <>
Date: Wed, 13 Jul 2011 07:18:49 +0100
List-post: <">>
Han Higasa wrote:
>Are you using a series protection resistor in series of HV capacitor 
>and the cold end of plate RF choke?
>30 - 50 ohm 50 - 100 W resistor is enough to protect diodes, IP 
>metering circuits and tubes etc.
>Any arc from HV to the ground is the same state as a short. With this 
>resistor arc remain small and short and put no damage on these 
>circuits. I am using two EDHD15K HV diode packs and a 50 ohm 100W 
>resistor on high-side of HV line for many years.
>A kit from GM3SEK also has this type of protection resistor.

Sorry, that isn't correct - I strongly RECOMMEND this surge limiting 
resistor, but I do not supply it in my kits because most builders prefer 
to find their own.

Dave has already shown that his specific problem is somewhere between 
the transformer, the diode stack and the reservoir capacitor (the 
transformer is the prime suspect). Since a surge resistor should always 
be connected *after* the reservoir capacitor, it cannot be relevant to 
Dave's problem.


73 from Ian GM3SEK
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