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Re: [Amps] gs-35b bias pb?

Subject: Re: [Amps] gs-35b bias pb?
From: Steve Thompson <>
Date: Tue, 28 Aug 2007 12:31:46 +0100
List-post: <>

Flo wrote:
> hi,
> i'm building my first tube amp on 2m with a gs-35b grid grounded.
> yesterday i made a try with the full bias circuit but when the ht (3500) 
> arrives the grid meter jump quite high then the fuse of the power supply 
> blown. I replace the fuse with a smaller one, i removed the bias circuit 
> and i have connected a 10K resistor between the cathode and the -HT. 
> Same result. I do not understand why the tube is not blocked  and why i 
> have  so many current on the grid.
> any idea ?
Something is allowing conduction between the anode and grid. Maybe gas 
inside the tube, maybe cathode material on the grid, maybe a short.

Try following the instructions here: 
to see if there is any improvement. You need to be able to apply a 
variable voltage through a high value high voltage resistor for safe 

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