In preparation for upgrading to Revision B, I just changed from firmware MCU 2.01, IOC 1.02 to 2.03/1.07. In the process, I lost my sidetone. I tried changing sidetone source as suggested, but don't get anything with either source. All other indications normal. No other mods done to the rig, other than the 160 board. SN 2636. Thanks in advance for possible help. Parker WD8JOL