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[AMPS] MEASURING FILAMENT VOLTAGE

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Subject: [AMPS] MEASURING FILAMENT VOLTAGE
From: ToddRoberts2001@aol.com (ToddRoberts2001@aol.com)
Date: Sun, 21 Oct 2001 20:41:22 EDT
I'm not sure if this has been brought up before, but wouldn't the best way to 
get a truly accurate reading of filament volts on a glass tube like a 4-1000 
would be to solder small wires directly to the filament pins and run them to 
an accurately calibrated AC voltmeter? There can be a small amount of 
resistance where the socket grips the tube pins and in a high-current 
filament circuit even a small resistance can drop the filament voltage some 
fraction of a volt? Is it feasable to measure the filament voltage at the 
pins in an operating GG amplifier where the filament circuit is above ground 
hot with RF? I would think using a pair of small RF chokes at the pins would 
isolate the AC voltmeter from the RF but could they cause problems with 
making the circuit unstable? Has anyone ever done this? Thanks for any 
comments. 73 Todd Roberts WD4NGG .

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