[Amps] FW: 4-1000 Bias

[Fuqua, Bill L]

________________________________________
From: Fuqua, Bill L
Sent: Friday, March 04, 2011 12:15 AM
To: Robrk
Subject: RE: [Amps] 4-1000 Bias

      I would find out why the there is a no-signal grid current.
Something must be wrong with metering circuit or there is some RF drive but any sort of parasitic oscillation usually
produces loads of plate current.
      If I recall at around 5.5kV or 6kV with zero volts bias and no drive the plate dissipation
does get close to 1kW.  Makes for a nice glow. But as soon as you provide some drive
the plate glow drops indicating a decrease in dissipation.

________________________________________
From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of Robrk [robrk at nidhog.net]
Sent: Wednesday, March 02, 2011 5:09 PM
To: Wayne Rogers
Cc: <amps at contesting.com>
Subject: Re: [Amps] 4-1000 Bias

Why is there "no signal" grid current?

Sent from my iPad

On Mar 1, 2011, at 12:38, "Wayne Rogers" <n1wr at chesapeake.net> wrote:

> I have a 4-1000 g-g homebrew amp.  It was designed 4000 volts on the plate.
> My new supply is 5500 volts under load.
>
> With the grid at ground potential and at 4000 volts on the plate the no
> signal grid current is 40 mA. and the plate current is 170 mA, which seems
> right.
>
> At 5500 volts on the plate and the grid at ground potential Ig is 80 mA. and
> Ip is 300 mA. which seems a bit high. My plan is to add bias to the grid.
> How do I determine what the correct operating point is for grounded grid?
> At 300 mA. I'm dissipating .3 X 5500 = 1650 watts which is way over the
> tubes rating.
>
> Thanks,  Wayne N1WR
>
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