Another thought: 

Maybe the driver is not seeing the oscillator and breaks into oscillation
at max gain. Check that the oscillator is working. Pull the oscillator
tube and see if it does the same thing. Be sure the VFO is outputting
several volts at the correct frequency, that the crystal/VFO switch is in
the VFO position (don't ask me how I know), That the crystal/VFO switch
is working. Check that you have adequate drive to the driver grid.  Good
luck.

73, Ed Richards K6UUZ

On Sun, 18 Jul 2004 16:19:43 -0700 Edward B Richards <[EMAIL PROTECTED]>
writes:
> Hi Gary, et al:
> 
> This is the way an oscillator acts. Check to be sure the VFO is not 
> going
> in and out of oscillation. It is also possible that the driver or PA 
> is
> going in and out of oscillation. Good luck.
> 
> 73, Ed Richards K6UUZ
> 
> 
> On Sun, 18 Jul 2004 18:22:20 -0400 "Gary Poland" 
> <[EMAIL PROTECTED]>
> writes:
> > I have tried a new 12BY7A and 5763 with no change. With the DX100 
> in 
> > CW and
> > the PLATE switch off...I have to run the DRIVE pot fully CW before 
> 
> > the GRID
> > current shows on the meter. Once peaked with the DRIVER TUNE and 
> set 
> > at 5 ma
> > all is well until I run the DRIVE pot back down CCW. Then running 
> it 
> > back up
> > results in no grid current until I max out the pot again. This 
> will 
> > also
> > occur if I move the DRIVER capacitor off peak. I always have to 
> max 
> > out the
> > DRIVE pot Really screwy HI HI.
> > 
> > 73, Gary
> > 
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