microphone hum

Phil wrote:
> Jerry Avins permanently inked into the cyberlog:

   ...

>>Either the wire is continuous or it isn't. A piece of #30 is enough.
>>What does "as good as it should be" mean?
> 
> 
> There were some pinches but I don't think I am correct about that.

?? You can't dim a light by tying knots in the cord.

(>>>I just checked my monitor and it is 68.76khz and vert 85.22 hz.  But)


>>>I believe I was near the tv when it showed humming.
>>
>>Clearly. That's the only source of 15,750.
> 
> 
> I'm not clear on how high freq alias but do you mean the 68.76 is
> aliased as 15.75

No. I mean that a TV display is the only likely source of 15,750.
  (525 lines/frame) * (30 frames/second) = 15750 lines/second.

   ...

>>Bingo! The microphone pellet isn't grounded? Then it's an antenna of
>>sorts. Tie it to the cable shield or put in a shielded container.
> 
> 
> Ok, I suspect something was amis there, I had played with various things
> along with touching the case, and I did notice shorting the ground to
> the case relieved it, also there is a small tab to the case near the
> ground solder joint and It appears it should have been part of the
> ground joint or not, I wasn't sure and now you've helped me there.
> 
> Can I solder it or will I destroy the condenser.  Its close enough to
> the case, about 1 mm, that I should be able to do it.

That tab was probably a spring contact, which means they didn't dare 
solder. (Heat can depolarize an electret.) Twist bare wire around the 
pellet leaving a tail, and solder to that.

   ...

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

Jerry Avins permanently inked into the cyberlog:

> Phil wrote:
>> Jerry Avins permanently inked into the cyberlog:
>
>    ...
>
>>> Either the wire is continuous or it isn't. A piece of #30 is enough.
>>> What does "as good as it should be" mean?
>>
>>
>> There were some pinches but I don't think I am correct about that.
>
> ?? You can't dim a light by tying knots in the cord.


ho, I meant I was wondering if the pinched wire had broken the shielding
connection and it may have been a compromised connection but I don't
think so since moving the wire doesn't cause the hum.

>
> (>>>I just checked my monitor and it is 68.76khz and vert 85.22 hz.
> But)
>
>
>>>> I believe I was near the tv when it showed humming.
>>>
>>> Clearly. That's the only source of 15,750.
>>
>>
>> I'm not clear on how high freq alias but do you mean the 68.76 is
>> aliased as 15.75
>
> No. I mean that a TV display is the only likely source of 15,750.
>   (525 lines/frame) * (30 frames/second) = 15750 lines/second.
>
>    ...
>
>>> Bingo! The microphone pellet isn't grounded? Then it's an antenna of
>>> sorts. Tie it to the cable shield or put in a shielded container.
>>
>>
>> Ok, I suspect something was amis there, I had played with various
>> things along with touching the case, and I did notice shorting the
>> ground to the case relieved it, also there is a small tab to the
>> case near the ground solder joint and It appears it should have been
>> part of the ground joint or not, I wasn't sure and now you've helped
>> me there.
>>
>> Can I solder it or will I destroy the condenser.  Its close enough to
>> the case, about 1 mm, that I should be able to do it.
>
> That tab was probably a spring contact, which means they didn't dare
> solder. (Heat can depolarize an electret.) Twist bare wire around the
> pellet leaving a tail, and solder to that.
>
>    ...
>
> Jerry



ok, I'll give that a go, thanks a lot.
-- 

Phil

I messed with it too much and the signal wire broke, So instead of
pitching it I resoldered it and the ground and now it works, no more
hum.  I guess the heat didn't affect it.


Jerry Avins permanently inked into the cyberlog:

> Phil wrote:
>
> That tab was probably a spring contact, which means they didn't dare
> solder. (Heat can depolarize an electret.) Twist bare wire around the
> pellet leaving a tail, and solder to that.
>
>    ...
>
> Jerry

-- 

Phil

Phil wrote:
> I messed with it too much and the signal wire broke, So instead of
> pitching it I resoldered it and the ground and now it works, no more
> hum.  I guess the heat didn't affect it.

Good fix!

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������