[Elecraft] KX1: Replace R30 22 Ohms with 33 Ohms?

[Ron D'Eau Claire]

R30 is a swamping resistor in the base of the final stage that holds the
gain down and so keeps the stage from being over-driven and/or having =
enough
gain to become unstable. It sounds like variations in the hFe of the =
output
transistor are responsible for some of the power variations that are =
being
reported, since increasing the drive by raising the value of R30 fixes =
the
problem.

Now, if the hFe of the final is low, then raising the value of the =
resistor
shouldn't cause a problem. What I'd be concerned about is whether the =
stage
remains unconditionally stable if the final has a high hFe and the value =
of
that resistor is raised - allowing it to exhibit even greater gain.=20

My "guess" would be "yes", since the drive pot (R4) is in parallel with =
that
resistor. So for a transistor with higher gain one would turn the pot so =
the
wiper is closer to the ground end of the pot to reduce the drive and =
keep
the output power at  the right level. Turning R4 to reduce the drive =
reduces
the resistance to ground and improves the stability of the stage.

The tricky part would be if someone tried to "QRO" their KX1 by
reducing/removing that transistor in order to get more than the rated
output. Not only would the stage have higher gain, the output matching
circuit wouldn't be optimum any longer which promotes instability as =
well.

My KX1 has rated output (with R30 at max where Wayne suggested putting =
it)
and I don't have any spare finals around to try if it gets unstable, so =
I
haven't tried it myself.=20

Ron AC7AC

-----Original Message-----

Since I'm still in the process of building, and will likely finish this=20
weekend, I am curious whether or not to do this replacement on my KX1.

How many KX1 builders have noted the low power out and made the change=20
described below?  I'd rather "replace" it before installing it  <grin> =20
And I can buy the replacement tomorrow.

TIA es 73, Phil