[Elecraft] K3 Hum on Audio...

[goldtr8 at charter.net]

Hi Phil,

I am no expert by any stretch of imagination if you follow my posts from 
my previous problems.

So please take what I have to say as only a suggestion.   Are all your 
external equipment grounds to a single point, this was major improvement 
in my shack.  What I mean by single ground is the grounding lugs for 
every piece of equipment in my shack goes to one grounding point so 
everything should be at the same potential.

Others who understand this more than I do will correct the 
implementation I am suggesting if I don't have it quite right.

Cheers
Don



~73
Don
KD8NNU


On Fri, Jan 13, 2012 at 12:20 PM, Phil Hystad wrote:

> Ron,
>
> I have been able to do more tests.  Unfortunately, it is in both mics 
> but not as strong in the Yamaha CM500 mic as in the MH2 but it is 
> present.
>
> This morning I double checked all connections (most in the back). 
> This includes the key out to the KPA500, the plugs for the cm500, the 
> external speaker, my foot PTT switch, and even the svga cable to the 
> KPA500.  Nuts, have not tested the serial port yet.  However, 
> absolutely no difference in behavior.   I can hear the hum on the 
> speaker when I have the monitor gain cranked up a little bit and 
> keying the mic in Test mode.
>
> If I lay my hand on the top of the K3 the hum disappears.  If I lay my 
> hand on the P3 sitting next to K3 the hum disappears but not as much. 
> And, I can do the same with other grounded equipment.  I have checked 
> my grounds and they all seem to be pretty good.
>
> So, I am at a loss as to what to try next.  This seemed to start on 
> its own Wednesday afternoon after my last SSB QSO.  I say that because 
> after that QSO, I turned the rigs off and then the next day (Thursday, 
> yesterday) I turned the rigs on and the hum was there on my first SSB 
> QSO at 6:30 PM.
>
> It sure seems like a grounding problem but I am not sure where to 
> check next.  Also, this problem arose mysteriously close to me setting 
> up the KPA500 which I put on the air for the first time Wednesday 
> early afternoon, CW first and then a few SSB QSOs and I got good audio 
> reports from both of those QSOs.  The hum though is definite, if 
> someone were listening to my audio with this hum they would hear it.
>
> 73, phil, K7PEH
>
>
> On Jan 13, 2012, at 8:12 AM, Ron D'Eau Claire wrote:
>
>> Since it goes away when changing mics, it sounds a lot like a broken
>> connection in the microphone connector. I used to fix those by the 
>> dozens on
>> shipboard VHF radios, equipped with hand-held mics. The complaint 
>> would be
>> transmitting hum, no audio, or no PTT action, depending upon which 
>> wire
>> broke.
>> Usually the break was at the connector, but sometimes it's in the 
>> mic,
>> depending upon which end had the best strain relief. Even found a 
>> broken
>> wire inside the cable on rare occasions.
>> 73,
>>
>> Ron AC7AC
>>
>> -----Original Message-----
>> Subject: [Elecraft] K3 Hum on Audio...
>>
>> When the sun rose today and it seems that my K3 decided to put some 
>> hum on
>> my audio.  During a quick SSB contact tonight on 80 meters I was told 
>> there
>> was hum on my audio.  This surprised me because yesterday I was 
>> involved in
>> two different SSB QSOs where I was particularly interested in audio 
>> reports
>> because I had just put the KPA500 on the air and wanted to know how 
>> it
>> sounds.  The audio reports yesterday, two different QSOs, were 
>> excellent.
>> In fact one person wanted to know the rig because he said it sounded
>> exceptional.
>>
>> Well, tonight, I get a report of what sounds like (the other guy 
>> reported)
>> 60 cycle hum on my audio.  Now, absolutely NOTHING is different from
>> yesterday, same configuration and all.  So, I am thinking maybe it 
>> has
>> something to do with the KPA500.  So, I put that in Standby and the 
>> hum is
>> still there on the audio.  The mic is the MH2 hand mic plugged into 
>> the
>> front of the K3.
>>
>> So, I switch to my Yamaha CM500 headset and mic plugged into the rear 
>> of the
>> K3.  No hum on that.  So, the hum seems to do with the MH2 or maybe 
>> the
>> front panel connection or something else.
>>
>> Does anyone know of what would cause this sudden thing and where I 
>> might go
>> to scope out the problem?  I would be more suspicious if it were some 
>> rig
>> that was new to me, or some mic that was new or something.  But, it 
>> is not
>> new and until now I have always had excellent reports.  Like I said,
>> yesterday the KPA500 was put on the air for the first time but the 
>> reports
>> were excellent reports on audio, this problem appeared today in fact, 
>> about
>> 30 minutes ago.  I turned the rig on at 6:15 PM and had the first QSO 
>> where
>> the hum was reported at 6:25 PM.
>>
>> 73, phil, K7PEH
>>
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