The main IC for the KIO3 board is the RS-232 Level Converter, U1. Part most likely to fail due to ESD / Static / External events. Texas Instruments SN75C1405 (U1), 16-pin Surface Mount. ... a version of the MAX232 with ESD may cross reference. Board photos http://www.elecraft.com/K3/mods/AF_Output_Mod_Rev_C.pdf Sent from iPad Air