K2 Excessive Internal Noise?

[Howard W. Ashcraft]

After solving an Auxbus issue with the KPA100, I noticed the following.
With no antenna, or a good dummy load, if the RF level is full counter
clockwise and the AF full clockwise you get a perfectly acceptable level
of audio hiss.  However, as you advance the RF level to 12 O'clock a
"bacon frying" noise starts to be perceptible.  At full RF, full AF, it
is quite distinct.  I don't seem to recall the "bacon frying" noise
before and it is low enough that band noise will blank it.  Also, I
rarely have the AF past 12 O'clock in operation, so it isn't apparent,
but I also think that it shouldn't be there.  Years ago I used to work
on audio equipment and this sounds like a noisy resistor, but because it
is coming out of the RF circuitry, it could be a few other things, too.
First question.  Would someone do a similar check on their K2 to see if
this is inherent (i.e., am I chasing rainbows).  Thanks in advance.
Second, I'm starting to go through the schematics looking for suspects
and will do a little testing when I get back home (on a business trip
right now).  If anyone has already experienced and addressed this, I
would appreciate your information to jump start my tracing.

Thanks,

Howard W1WF



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[Dan Barker]

On mine, (K2 #2456, Audio Pot Mod done), the radio is silent with AF Max and
RF Min. Hiss occurs (very steady, not like bacon) beginning about 2:00
O'clock on the RF and is very low level even fully CW.

It's very hard to know what amplitude you are experiencing. My o'scope says
30 mv P-P across an 8 ohm speaker in the Ext Spk. Jack with both knobs fully
CW.

hth

Dan / WG4S

<snip>
At full RF, full AF, it is quite distinct.  I don't seem to recall the
"bacon frying" noise before and it is low enough that band noise will blank
it.  Also, I rarely have the AF past 12 O'clock in operation, so it isn't
apparent, but I also think that it shouldn't be there.
</snip>

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