i'm having trouble at our church with the phantom power mic. i can't seem to get any volume out of it. if i turn it up it just seems to squeel and i've adjusted the equilizer a couple of times and it still squeels before i get volume. it worked great a couple of moths age but has slowly gotten worse. i've tried different cords and all of our non-phantom mics work well. do phantom mics go bad or could our phantom power be going bad in the board? Is there a way to test this or am i looking at this wrong?