A quick test to identify the possible area of trouble is to put the radio into the "PA" mode and plug an external speaker into the PA speaker jack on the back of the radio, with the mic. gain all the way up and the radio volume control about halfway up. Then, try keying up and talking. If you hear yourself, the problem is probably in the transmitter section or the microprocessor or switching circuits. If you don't hear yourself, it is probably something in the audio section, either amplification or switching. Before doing this test you should make absolutely sure you have a known working microphone connected to the radio and a known working external speaker. Your trouble could also rest under bad solder joints or the aftermath of someone working on the radio previously that left this present. You did not say if you had receive audio in your complaint which is helpful to know along with, is the carrier produced on frequency with what your radio display says. The microphone is always the #1 suspect with your description.