On Tuesday, March 26, 2013 8:35:26 PM UTC-4, Dan Marotta wrote:
Reception is good and, until recently, transmission has been good, as well. Lately, transmission has been intermittent. The radio transmits carrier, but no modulation. I have gotten a few false starts since one time moving the boom microphone caused it to transmit again. Thinking of frayed, chafed, or broken wires, I dismantled the mic but found nothing wrong. Looking further, I found numerous splices in the mic wire and I'm in process of replacing it in its entirety. With the mic wires cut, I measured around 9.5 Vdc between the conductor and the shield (pins 1 and 2 of the DB15 connector. A friend happened by and told me that he had heard that Microair radios of my vintage had a known problem wherein there were two circuit boards mounted at right angles to each other and, over time, vibration could cause a connection to break. Has anyone else heard this? Is there a Microair repair facility in the US? Thanks, Dan, LAK-17a, 5J

This is a common symptom of a problem with the socket that the main processor chip seats in. There was a tech note on how to clear this symptom by removal, cleaning of contacts, and reinstalling.
A later service bulletin defines a more permanent fix to be done by repair shops.
UH