Dead microphone CAD m177

Monkey Allen

Fork and spoon operator
I think I killed my CAD m177 condenser mic...the best mic I own.

I was setting up and learning how to use a Fireface UC and I had the 48v engaged and also had 65db gain dialled in.

I heard a sucking kind of noise from my speakers along with a popping noise I suppose. It happened fast...but I think I plugged the mic in cold with the 48v and 65db on.

Anyway...the mic was and is now completely unresponsive...except for a very small surge in the VU display of my preamp when I plug it in and up the gain. But after that second or so...nothing.

Does anyone know what the ballistics of a dead mic are under these circumstances? Is it a case of a severed wire (that'd be good because even I could fix that)...or have I more likely blown some kind of capacitor or circuit component on the circuit board?

Bit of a shame...cost me about $300 back in its day

thanks
 
I recall the M177 has an opamp output. Most opamps don't like to have 48V on their outputs, so the mic has to have protection circuitry. Thus, the likely causes of failure are:

- a fault in a protection component (diode or a cap) causing power loss or other failure
- a failure in/lack of protection component causing failure of output opamp
- some other cause

First step is contact CAD to see if they can help with repair, or at least provide a schematic. If you don't have CAD repair it and want to try yourself, you follow along the schematic and measure DC voltage until you find a value that is not correct, that will tell you the component that has failed.


PS the gain setting on the preamp has no effect on the microphone.
 
Thanks for that info...funnily enough it works now...that's the second or third time since I bought it 5 or so years ago I've thought it was dead only to have it come back a day or so later.
 
I had a Large duel diaphragm condenser that did the same thing your CAD is going through. Works one day and doesn't the next. Come to find out there was a contaminate between the two plates that just needed to be cleaned away and they stopped shorting out.
 
Yeah could be anyo of those things....but the only times when it hasn't worked are when I've done something stupid like plug it in fully charged or something weird....it's hard to recall the exact state when it fails...but the 2 or 3 times it's failed have been when I've done something unusual. Usually I would be careful about the state in which I plug or unplug it. Anyway...it's perfectly fine now.
 
I recently had a Rode NT1000 that would work for a few seconds then stop, then work again after a min or so, it was a faulty capsule that they replaced for free. So it could be a capsule problem.

Alan.
 
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