Phantom mic

Phantom Mic is high sensitive microphone and I never seen one that gone bad but that I guess relates to handling and pre-causions.

Mic should not be close to speakers or it'll generate feed back from the speaker, proper volume control should be apply to the speakers and to the mic mixer to get optimum performance.

Check your tone control, try to elimanate other sources of audio first when testing the mic in question. Gradually adjust volume of the speaker/s with the mic level set at 35% then increses till it'll squeel. Then turn speaker level down till no more squeel. Do the same test on the mic this time introduce voice to the mic.

If all test fail then try using other mics and compare. Try other wires as well and try not using extension. Check your mic mixer other controls, posible controls was set un-notice.