Cary,
I battled a hum/buzz problem just two weeks ago. After almost a full day spent
hunting, experimenting, searching, and doing everything under the sun plus some
very helpful dialog from others here on Elecraft forum, the hum/buzz was
finally fixed.
I did not fix it, it just disappeared. So, here are some things I did...
(1) I did all my tests with the monitor on and TX in TEST mode since that in
itself showed the hum/buzz.
(2) With the help of Jim Brown (K9YC) I used the TX EQualization feature of
the K3 to crimp down to minimum
the low frequencies of the hum/buzz. Doing this, it appeared that this
was indeed a buzz and not a 60-cycle
hum because the buzz did not start to be attenuated until after the 400
Hz TXEQ was set to zero and I started
working on the next higher frequency band.
(3) I was confused as to whether this was front mic and back end mic inputs or
just front. I finally determined that
this was on the front mic only with 98 percent confidence. It is not 100
percent confidence because all of my
experiments to prove one way or the other were a bit scrambled but I
think this was front panel mic only.
(4) I then focused on the mic itself, an Elecraft MH2 hand mic. Unfortunately
it was the only mic I had for the front
panel but if you have more then one then I definitely suggest you test
them all to see if the hum/buzz is
independent of mic.
(5) I jiggled and bumped this front panel mic and connector to see if there
was some loose connection. Someone
suggested florescent lighting as a noise generated and I tested with all
lights turned off (see next point).
(6) I also had a nice 13.8 Li-nanoPhosphate battery so I disconnected
EVERYTHING from the K3. The only two
things connected were the 13.8 volt battery on the power and the mic on
the front panel. No Antenna, no
ground, no other connector to the K3. Hum/Buzz was still there and in
that test I also turned off the circuit
breaker for all AC in my shack. Did not help.
(7) After some tests, and other things, the hum just seemed to disappear and
never came back since. My best
guess is that it was one of the following: (1) either an external noise
source that eventually turned off and
my front panel mic was just more susceptible to picking it up; or, (2)
the front panel mic itself had some kind
of loose connection that just seemed to finally correct itself. I favor
cause (1) though. I am kind of hoping it
comes back so I can test some more.
73, phil, K7PEH
On Jan 23, 2012, at 7:37 AM, Hunsdon Cary III wrote:
> Don:
> You know it's hard to tell the difference between a buzz and a 60 hertz
> hum, at least to my 66 year old ears. HOWEVER, when I disconnected the mic
> front the front panel connector and used the XMIT button on the front panel,
> there is no buzz or hum! I'll start troubleshooting the mic cable now!
> Tnx for your help.
> 73,
> Cary, K4TM
>
> On Jan 23, 2012, at 10:23 AM, Don Wilhelm wrote:
>
>> Cary,
>>
>> Is it hum or is it actually "buzz"? Hum is 60 Hz AC, but buzz will be of
>> various frequencies, and it is difficult to tell them apart with just your
>> ears as detectors.
>>
>> Does it disappear if the microphone is not connected? Use XMIT to put the
>> K3 in transmit while you are listening. If it is only when the microphone
>> is connected, you may have a broken wire in the mic cable.
>>
>> 73,
>> Don W3FPR
>>
>> On 1/23/2012 10:10 AM, Hunsdon Cary III wrote:
>>> K3 Experts: My K3-100 has been flawless in its performance until
>>> yesterday. I had a schedule with W5ZNN who told me I had a hum on my
>>> signal; I put my headphones on and sure enough there it was on transmit. I
>>> tried plugging the Astron 35M directly into the AC outlet instead of the
>>> outlet strip - no luck, hum was still there. I connected the K3 to my SEC
>>> 1223 switching power supply and, you guessed it, the hum is still there. I
>>> hate to think there's something amiss with the K3 but it looks that way.
>>> Any ideas?
>>> 73,
>>> Cary, K4TM
>>> Lynchburg VAh
>>> [email protected]
>>>
>>>
>>>
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>
> H. Cary III
> [email protected]
>
>
>
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