[Amps] GS-35b 2 meter amp - plate capacitor spacing from tube?

[Bill Dzurilla]

Thanks to all who replied.  I was able to extend the plunger, and output increased to 850 watts, with 50 watts drive.  And I was able to find a dip.
The only thing that seems odd is that the plate current meter is still reading just 230 ma.  That can't be right.  With plate voltage of 3300v, there has to be about 500 ma to get 850 watts output.

73, Bill


> > Bill, with plate current that low, the plate load
> impedance is pretty high.
> > To match a higher impedance requires less coupling C.
> Less coupling C
> > means you  need more tune C to keep the plate
> circuit in resonance.
> > 
> > If you increase the drive level, the plate current
> will rise and the plate
> > load impedance will be lowered which will call for an
> increase in coupling
> > C and  a reduction in tune C.
> > 
> > If you are unable to increase the drive power, then
> yes, you need to change
> > the tune C plunger to allow more tune C to be
> available.
> > 
> > 73,
> > Gerald K5GW
> > 
> > 
> > 
> > 
> > In a message dated 6/10/2010 3:54:09 P.M. Central
> Daylight Time,
> > billdz.geo at yahoo.com
> writes:
> > 
> > Any  Russian tube experts on this board?
> > 
> > Picked up a homebrew GS-35B 2 meter  amp, seems
> to be working OK, about 650
> > watts out with 50 watts drive from my 
> FT-847.  The anode is tuned with a
> > piece of copper that is pushed closer  to the
> tube or further away by a
> > plunger controlled by a knob on the front 
> panel.  Power was still going up when
> > the plunger reached its maximum  push on the
> copper, which leaves the copper
> > about 3/4" (20mm) from the  tube.  Do you
> think perhaps the plunger needs
> > to be extended to get the  copper closer to the
> tube for best output? Plate
> > voltage is 3300v, plate  current only about .23
> amps.
> > 
> > 73, Bill NZ5N/OM9ACA
> > 
> > 
> > 
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