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Dead SM-48s



 
 
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  #1  
Old December 1st 18, 02:15 AM posted to rec.audio.pro
Ron C[_2_]
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Posts: 244
Default Dead SM-48s

Story and minor rant:

I was asked to do sound for karaoke at a local VFW.
I pulled out some old SM-48s .. figured they'd be
adequate for that job.

When I checked them out they were all dead, no
sound what so ever.

[OK, I got the job done with other mic's ]

Anyway, later I pulled the top off the the 48's
and found the foam had turned to sticky goo.
Cleaned out the goo as best I could .. but still
dead.

So... I figured I could just replace the capsules.
Looked up the price and found they'd cost more
than new SM-48's!

Duh, this just doesn't seem right!

Anyway, I have a few nice SM-48 bodies,
hate to just throw them out .. any suggestions?

~~
OK, just lightly venting. End of minor rant.

--
==
Later...
Ron Capik
--


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  #2  
Old December 1st 18, 03:18 PM posted to rec.audio.pro
Klay Anderson[_3_]
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Posts: 1
Default Dead SM-48s

Send them back to Shure. They’ll give you new ones for the price of repair or better.
  #3  
Old December 2nd 18, 12:35 AM posted to rec.audio.pro
PStamler
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Posts: 873
Default Dead SM-48s

On Friday, November 30, 2018 at 7:15:44 PM UTC-6, Ron C wrote:
>
> Anyway, later I pulled the top off the the 48's
> and found the foam had turned to sticky goo.
> Cleaned out the goo as best I could .. but still
> dead.
>
> So... I figured I could just replace the capsules.
> Looked up the price and found they'd cost more
> than new SM-48's!


Welcome to the economics of the modern microphone business.

Have you checked whether there's a break in the inteqrnal wiring?

Peace,
Paul
  #4  
Old December 2nd 18, 02:13 AM posted to rec.audio.pro
Ron C[_2_]
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Posts: 244
Default Dead SM-48s

On 12/1/2018 6:35 PM, PStamler wrote:
> On Friday, November 30, 2018 at 7:15:44 PM UTC-6, Ron C wrote:
>>
>> Anyway, later I pulled the top off the the 48's
>> and found the foam had turned to sticky goo.
>> Cleaned out the goo as best I could .. but still
>> dead.
>>
>> So... I figured I could just replace the capsules.
>> Looked up the price and found they'd cost more
>> than new SM-48's!

>
> Welcome to the economics of the modern microphone business.
>
> Have you checked whether there's a break in the inteqrnal wiring?
>
> Peace,
> Paul
>

Yes, I've checked .. no problems there.
Heck, the mic's are 20++ years old, so I guess
I've gotten my money's worth out of them.

I understand that electrets can become depolorized
but never thought dynamics would/could go bad just
sitting in a box. Live and learn.
--
==
Later...
Ron Capik
--


  #5  
Old December 2nd 18, 12:55 PM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 364
Default Dead SM-48s

Ron C wrote:
>
>
> >
> > Have you checked whether there's a break in the inteqrnal wiring?
> >
> > Peace,
> > Paul
> >

>
> Yes, I've checked .. no problems there.
>


** Hang on - you say the internal wiring is all OK ( not corroded) and the mics are both dead ? Have you checked the voice coil with a DMM ?? A reading at the XLR of about 250 ohms shows it is intact.


> Heck, the mic's are 20++ years old,



** Still within the useful lifespan for Shure vocal mics that get low usage.


> so I guess
> I've gotten my money's worth out of them.
>


** I disagree and think the foam wind sock disintegration is a separate issue to the mics going silent.


> I understand that electrets can become depolorized
> but never thought dynamics would/could go bad just
> sitting in a box. Live and learn.



** Fine copper wire, as normally used for voice coils on mic diaphragms, corrodes under damp conditions and develops opens.

However, Shure mics like the SM57 & SM58 use much thicker wire for the voice coils followed by a step up transformer which goes a long way to extending these mics lives.



.... Phil


  #6  
Old December 2nd 18, 03:47 PM posted to rec.audio.pro
Ron C[_2_]
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Posts: 244
Default Dead SM-48s

On 12/2/2018 6:55 AM, Phil Allison wrote:
> Ron C wrote:
>>
>>
>>>
>>> Have you checked whether there's a break in the inteqrnal wiring?
>>>
>>> Peace,
>>> Paul
>>>

>>
>> Yes, I've checked .. no problems there.
>>

>
> ** Hang on - you say the internal wiring is all OK ( not corroded) and the mics are both dead ? Have you checked the voice coil with a DMM ?? A reading at the XLR of about 250 ohms shows it is intact.
>
>
>> Heck, the mic's are 20++ years old,

>
>
> ** Still within the useful lifespan for Shure vocal mics that get low usage.
>
>
>> so I guess
>> I've gotten my money's worth out of them.
>>

>
> ** I disagree and think the foam wind sock disintegration is a separate issue to the mics going silent.
>
>
>> I understand that electrets can become depolorized
>> but never thought dynamics would/could go bad just
>> sitting in a box. Live and learn.

>
>
> ** Fine copper wire, as normally used for voice coils on mic diaphragms, corrodes under damp conditions and develops opens.
>
> However, Shure mics like the SM57 & SM58 use much thicker wire for the voice coils followed by a step up transformer which goes a long way to extending these mics lives.
>
>
>
> ... Phil
>
>

Damn, I hadn't thought to check for an open voice coil.
Yep, they both measure as open. Corrosion of the super
fine wire is quite the logical explanation.

Thanks.
--
==
Later...
Ron Capik
--
..
  #7  
Old December 3rd 18, 07:40 AM posted to rec.audio.pro
Phil Allison[_4_]
external usenet poster
 
Posts: 364
Default Dead SM-48s

Ron C wrote:
>
> Phil Allison wrote:
>>>
> >>>
> >>> Have you checked whether there's a break in the inteqrnal wiring?
> >>>
> >>> Peace,
> >>> Paul
> >>>
> >>
> >> Yes, I've checked .. no problems there.
> >>

> >
> > ** Hang on - you say the internal wiring is all OK ( not corroded) and the mics are both dead ? Have you checked the voice coil with a DMM ?? A reading at the XLR of about 250 ohms shows it is intact.
> >
> >
> >> Heck, the mic's are 20++ years old,

> >
> >
> > ** Still within the useful lifespan for Shure vocal mics that get low usage.
> >
> >
> >> so I guess
> >> I've gotten my money's worth out of them.
> >>

> >
> > ** I disagree and think the foam wind sock disintegration is a separate issue to the mics going silent.
> >
> >
> >> I understand that electrets can become depolorized
> >> but never thought dynamics would/could go bad just
> >> sitting in a box. Live and learn.

> >
> >
> > ** Fine copper wire, as normally used for voice coils on mic diaphragms, corrodes under damp conditions and develops opens.
> >
> > However, Shure mics like the SM57 & SM58 use much thicker wire for the voice coils followed by a step up transformer which goes a long way to extending these mics lives.
> >
> >
> >
> > ... Phil
> >
> >

> Damn, I hadn't thought to check for an open voice coil.
>


** Not a lot else makes a dynamic mic go silent.


> Yep, they both measure as open. Corrosion of the super
> fine wire is quite the logical explanation.
>


** I think Klay Anderson's advice is worth taking.

" Send them back to Shure. They’ll give you new ones for the price of repair or better. "

Shure may just send you two new SM-48s.



.... Phil
















 




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