i have just purchased this mic to find that when powered up via 48 volts Phantom it works for 2 seconds then fades and continues to work but at a much lower volume, like as if the fader was pulled down on the desk. can you please advise me what the problem might be and what year it was manafactured. It has a battery compartment in the body and a power indicator which shows that the phantom power is reaching the mic. Any help appreciated. many thanks Phil p.s. could it be dampness?