By this do you mean connect the DVM to check for voltage at the MCU's RX pin socket location on the EasyPic6 with the MCU removed? I don't undersand which serial pin #2 you are referring to. It seems to me that connecting to the RX socket location would also confirm whether the inverter chip is working as long as I know the cable is good. Would appreciate your clarification on that.
Serial pin#2 would be the RX from the test board. I did not know that you have an O scope.
Write a code to send serial data and connect your scope to the EasyPic board. That will tell you if anything is getting out.