Can't help you directly, but I can offer an alternative. The A200 is a great little radio, but the factory settings for Mic Gain and Sidetone are set way too high for our high-noise cockpits. Try adjusting the gain down a bit on one of the radios and see if that doesn't help. Both are controlled via pots on the top of the radio that are covered by little silver tape pieces.
This is a well documented issue with this radio.