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.
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Later...
Ron Capik
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