I had an overvoltage when the V regulator on my 172 failed. Now the headsets will not receive audio, but will transmit. When the speaker button is pushed on the Narco CP136M audio panel, the speaker functions for one radio only. The headsets checked good in another plane, and the intercom seems to function well. I feel the overvoltage fried some of the audio panel, but would like input. If it's fried, I need a Narco CP136M.