If your meter is in SERIES with the B- lead then all you are reading is
plate current. This is how I meter my amps for plate current, and it
requires a dedicated meter. On the other hand, if as you wrote:
"So with a GG triode, a meter in the neg lead of the power supply filter
caps to chassis ground, reads only plate current and not any grid current,
right?"
Then in this case your meter is in parallel with B- & ground and I
expect would read the sum of grid & plate currents. After all, the only way
to measure grid current in a GG triode, short of a meter in series between
the tube grid
and chassis ground, is to measure between chassis ground & B-. It also
doesn't
matter whether (for arguments sake anyway) B- is tapped at the filter caps,
FWB or cathode- it is still
a B- to ground connection based on what you wrote. This is where the
"float" resistor value is important because in such a configuration it is a
shunt for the meter which it is in parallel with. You also have to have a
calibration resistor with the parallel configuration.
Dave N3DB
----- Original Message -----
From: "Roy" <royanjoy@ncn.net>
To: <amps@contesting.com>
Sent: Tuesday, November 10, 2009 1:18 PM
Subject: Re: [Amps] B- questions
> Last stated,
>
>> Remember, the meter is not in the cathode to ground, but from filter caps
>> to
>> ground.
>
> "Measuring the power supply current you will read the power supply
> current
> through all
> tube/s elements. If there is a screen grid and you wish to measure all
> tube
> elements
> separately, the screen grid meter pretty much has to be in the screen grid
> connection.
> To the SG supply or to ground."
>
>
> The positive terminal of the power supply connects only to the triode
> tube's
> plate. Therefore only plate current can flow in the PSU's negative lead
> and
> meter it seems to me.
>
> Roy, K6XK
>
>
>
>
>
>
>
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