[Elecraft] Fw: k2 af gain control

[Ron D'Eau Claire]

John, that sounds like a "bad" pot. I say that in quotes because the pot =
may
be just fine in a more typical circuit, but the original Elecraft =
circuit
put severe constraints on the minimum resistance portion of the pot that
cause a lot of them to act up.=20

The gain control mod will help. It may even eliminate the need to change =
the
pot. At the very least, it will make the action of the gain control much
better, even if you do change the pot.=20

Here's why.

The original Elecraft AF gain circuit used the pot in an unusual way. =
The AF
pot was a shunt resistance across the audio channel. When you turned the
gain "down" you were literally shorting out the audio signal going to =
the
output amplifier. This worked okay in the majority of cases, but it =
depended
on a very low resistance across the pot at minimum and most ops found =
the
desired gain settings were very close to "minimum".=20

The mod rewires the pot circuit so it acts like a normal gain control. =
The
audio level vs. pot rotation is now logarithmic, like virtually any =
audio
gain control. That means that the normal operating point is well up on =
the
rotation of the pot while the total audio at "full volume" is not =
affected.=20

Because of the better control characteristic, the circuit does not =
require
the pot to show very low resistance at minimum volume, so a lot of pots =
that
were too "noisy" for the original circuit are FB in the new circuit.

Ron AC7AC
K2 # 1289

-----Original Message-----
 in 2001 wayne came out with a mod for the alternative wiring for the k2 =
af
gain control due to noisy pot. My serial # is 2444 and my pot is  =
showing
signs of noise and at the minimum setting it does show "leak thru".  But =
in
addition to this, it sometimes has no noise or signal at all and i  =
either
have to adjust the pot or turn the rig off and on quickly and then  the
sound returns.

 What does this sound like? Does this require the modification or just =
some
spray to the pot. Or does it sound like a loose connection and if so =
where
do you think i should check?

 john