[Amps] Measuring fil V

[Steve]

Good points, Jim. I stick with resistors as it avoids embarrassment 
if/when the meter wires get shorted. Been there, done that..... :-)

Steve G8GSQ

> 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