K2 scratchy volume control

[paul-292]

I have a K2, serial 2592 that has recently developed a noisy volume
control and turning the RF gain causes the AGC to jump.  Guessing the RF
control is noisy also.

I disassembled the K2 thinking I could spray a cleaner in the controls -
but there are no openings in the pots.  So these pots need to be replaced
- what do you recommend?

Note: I did the volume control mod several years so that doesn't need to
be done.

Thanks,

Paul
AD5IW
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[Don Wilhelm-4]

Paul,

Install the Modified AF Gain Wiring (I believe you will find it on the
Elecraft website with the Application Notes for the K2), also if your
pot is already scratchy, I suggest you order a new pot, even if you
could get it in, the control cleaner is not likely to work for long.

73,
Don W3FPR

paul wrote:

> I have a K2, serial 2592 that has recently developed a noisy volume
> control and turning the RF gain causes the AGC to jump.  Guessing the RF
> control is noisy also.
>
> I disassembled the K2 thinking I could spray a cleaner in the controls -
> but there are no openings in the pots.  So these pots need to be replaced
> - what do you recommend?
>
> Note: I did the volume control mod several years so that doesn't need to
> be done.
>
> Thanks,
>
> Paul
> AD5IW
>  
>

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[gt-i]

Paul & Don,
I got the same problem despite I have applied the new AF wiring.
Especially the RF pot problem appeared last year all of a sudden.
Mechanically, the pot does not sound too bad.

Elecraft, pse, what is the explanation for this? Do we really need to
replace the AF/RF pots?

73
Gernot
DF5RF
K2#2329
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[Don Wilhelm-4]

Gernot,

I repair many K2s, both as an independent and as an Elecraft hourly
employee, so I believe I am qualified to speak to your comment.  I
cannot suggest that this is an "official" Elecraft response because I do
not have Eric or Wayne's permission on this particular situation, and I
do not have any data on the life expectancy for these controls.

.Most of the AF Gain pots are still good, although a scratchy one is
encountered occasionally.  Rarely do I see that in an RF Gain control,
but then many operators (likely most) just leave the RF Gain at max and
depend on the AGC, so it does not get as much use as the AF Gain control.
If the gain control has been used a lot, the track can wear out, and
replacement is the only certain cure that I know.

So from that perspective, the pots are of adequate quality for the
average K2.  Of the K2s that I repair, those that show obvious signs of
greater than average use (buttons worn, knobs show wear, etc) are the
most likely ones to have a bad AF Gain control.

With the unmodified AF Gain circuit in K2s below SN 3000, there was a
bit of current drawn through the AF Gain control which accelerated the
chance that the control would become scratchy, so if the AF Gain control
is already scratchy, adding the AF Gain alternate wiring mod will not
cure that condition.  The wiring mod is included on the boards for all
K2s above SN 3000 (now greater than 1/2 the K2s out there).

If you use the RF Gain control frequently it is possible that it may be
worn too.  You did not say  if you use the RF Gain frequently, or if you
operate the K2 more hours than the average ham.

73,
Don W3FPR

DF5RF wrote:

> Paul & Don,
> I got the same problem despite I have applied the new AF wiring.
> Especially the RF pot problem appeared last year all of a sudden.
> Mechanically, the pot does not sound too bad.
>
> Elecraft, pse, what is the explanation for this? Do we really need to
> replace the AF/RF pots?
>
> 73
> Gernot
> DF5RF
> K2#2329
>  
>

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