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Re: [Amps] Measuring fil V

To: amp <>
Subject: Re: [Amps] Measuring fil V
From: Ron W4BIN <>
Date: Wed, 8 Jun 2022 21:36:27 -0400
List-post: <>
   Randall, Randy wrote:

Possible stupid question alert.  Why not measure filament current instead of 
Then you do not have to worry about accounting for losses in the filament path 
or the
position of the voltmeter connection?  Or is there too much variability in the 
drawn from tube to tube to be useable?

  As a retired broadcast engineer I can tell you:  Some equipment manufacturers provide a high current shunt (100. Amperes or so for something like 62. Amperes) and a dedicated Ammeter for the monitoring the filament current of the final power amplifier tube.  When a new tube is installed the filament Voltage is adjusted to the final factory test value and that dc current is logged and that current is maintained
through out the life of that tube.  (dc current for lower noise)
Such power supplies frequently feature two 24." long nichrome rods with an adjustable
short between them as the filament Voltage and current adjustment.

   Ron  W4BIN - Understanding is much better than
                                      knowing how.MX

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