K2 RF Gain Control question

[T Gahagan]

I just noticed that whenever I touch my RF gain control knob for adjustment the S meter jumps completely to the right and VERY slowly drops to whatever level of RF gain I have set.  It takes several seconds for the receiver to come back to the point where it can receive again.  I have used other K2's and this has not been the case.  Can someone else tell me if they see this happening.  I probably haven't explained this very well but would be glad to explain this more if needed.

Thanks, WA7U
Todd
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[Ron D'Eau Claire-2]

Todd, that sounds like a "noisy" pot in which the wiper isn't making good
contact with the resistive element inside. When you touch it, the circuit
opens briefly, which is the same as turning the RF Gain all the way to
minimum. That will cause the S-meter to read full scale. The delay returning
to normal should be the AGC decay rate. If you tap AGC to switch to FAST, it
should recover much more quickly.

One fix is to put a few drops of a control lubricant on the control shaft
with the rig standing front panel upward so the lubricant will run into the
pot. Turn it a number of times to work it down into the resistive element. I
use Caig DeOxit for that. It comes in a small squeeze bottle with a hollow
needle applicator. Recommend you avoid any sprays. They get stuff all over
the place. If a spray is all you have, recommend you spray onto a small
screwdriver shaft or length of wire it to collect drops of liquid on the
wire or screwdriver shaft. Work away from the rig with a towel behind the
sprayer to catch the overspray. Then position the wet wire or screwdriver
shaft so the drops run down onto the pot shaft and into the pot itself.

If it's a stubborn case, you may need to replace the pot.

Ron AC7AC

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

I just noticed that whenever I touch my RF gain control knob for adjustment
the S meter jumps completely to the right and VERY slowly drops to whatever
level of RF gain I have set.  It takes several seconds for the receiver to
come back to the point where it can receive again.  I have used other K2's
and this has not been the case.  Can someone else tell me if they see this
happening.  I probably haven't explained this very well but would be glad to
explain this more if needed.

Thanks, WA7U
Todd

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[T Gahagan]

Thanks Tom,

I suspect the gain pot is defective.  I will check soldering also.  I'll get
an RF gain pot on the way and try swapping it out also.

Todd

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[Ken Kopp-2]

Spraying the chemical onto/into a "Q-tip" and
then squeezing it out by pressing the cotton
against the upward-pointing shaft will avoid the
splattering.  

73! Ken Kopp - K0PP (K2 #5665)
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[T Gahagan]

The lube is a good place to start Ron.  Thanks.  I have noticed that just
touching the RF knob causes this to happen so you are probably on to
something here.  I don't have a lube other than tri-flow but will look for
something like what you mentioned.  Todd

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[Rod Hotz]

How interesting. My #1126 K2 does exactly as you described Todd. Although I
rarely change the rf control level, I've always wondered why my K2 behaved
this way. It'll be interesting to see what kind of comments your question
brings.

73,

Rod
K5BGB
Licensed June 1955

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Todd Gahagan
Sent: Sunday, February 18, 2007 10:18 AM
To: Elecraft Reflector
Subject: [Elecraft] K2 RF Gain Control question

I just noticed that whenever I touch my RF gain control knob for adjustment
the S meter jumps completely to the right and VERY slowly drops to whatever
level of RF gain I have set.  It takes several seconds for the receiver to
come back to the point where it can receive again.  I have used other K2's
and this has not been the case.  Can someone else tell me if they see this
happening.  I probably haven't explained this very well but would be glad to
explain this more if needed.

Thanks, WA7U
Todd
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