[Amps] Measuring fil V

[Jim W7RY]

I'm always careful when having to use 10 KW resistors in the filament 
lines... I always keep one hand in my pocket on such occasions.  LOL

73, Jim W7RY


On 6/7/2022 11:58 AM, jim.thom jim.thom at telus.net wrote:
> Be careful if using a 10 kw resistor hanging off each cathode lug on a GG
> triode.
> That might work if using a true rms dvm..since the dvm has a high Z input.
>
> But if fed to an iron vane type of panel meter, you will end up with a
> massive V drop across both resistors.
>
> A pair of  low  dc resistance chokes, bypassed at cold ends to chassis, is
> dead simple.  Then another pair of bypass caps at panel mounted test jacks.
>
> Years ago, energy onix used RF chokes on one of it's  FM GG triode
> amps..and the dc resistance across the chokes was too high..and resulted in
> a vdrop.  When the fil V was tweaked for  'normal' under load, using their
> front panel iron vane meter, the actual V at the cathode was way too high.
>   This resulted in several premature tube failures.   And if a dvm was in
> parallel  with the panel meter, it too will read on the low side.
>
> Jim  VE7RF
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