[Elecraft] K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

[Joe Subich, W4TV]

The capacitor modification applied to fewer than 200 units shipped more
than six years ago.  It was identified early and most of the initial
production run were modified by the factory or distributors before they
ever reached an end-user.

73,

    ... Joe, W4TV


On 3/11/2014 6:21 PM, Stewart wrote:
> Tom,
> Check that your MKII has the capacitor modification that decouples the USB cable
> shield. If not,  RF on the cable can cause audio problems. Details are on the
> MicroHam site.
>
> 73
> Stewart G3RXQ
>
> On Tue, 11 Mar 2014 17:58:00 -0400, tomb18 at videotron.ca wrote:
>> Ok, thanks, that's what I thought. A little more complicated since I have a
> MicroHam microkeyer II in the circuit but probably fixable.
>>
>> 73's Tom
>>
>> On 3/11/14, "Donehrlich at q.com" <Donehrlich at q.com> wrote:
>>> Almost certainly RF getting into the mic circuit. Try a different mic .. or
> use the rear panel mic connector as a check. You probably have high SWR into the
> antenna feedline (or coax) after the tuner on 20 meters and that is why you only
> see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low
> swr .. it is AFTER the tuner where you have high SWR) results in high current or
> high voltage that then couples into other shack wiring. Of course, the higher
> power from the KPA500 pushes those voltages/currents to levels that are more
> likely to cause problems. Been there, done that .. many times.
>>>
>>> Don K7FJ
>>>
>>>
>>>> Ok,
>>>>
>>>> So my audio is quite distorted as I can hear in my headphones with the
> monitor. But this only happens on 20m and only with the KPA500 in operate.
>>>> Sound like RF? or is something else going on?
>>>>
>>>>
>>>> Thanks
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