Yes... the microphone case is ground...? blue wire is going to ground and continuity checks good to ground everywhere as best I can tell.? Even the metal part of the microphone shows dead short to ground.? The purple lead is going to the mic side.
I measure 31 mV on both sides of R60.? I get 3 mV on one side of C60 and 31 mV on the other side of C60.? The side closest to the connector is 31 mV.? Having the mic plugged or not makes no difference.? I've measured R60 in the circuit (I know... not always reliable)... it measures 4.68 K Ohms.
There are two mods I've made but shouldn't have any effect.? I've installed a DPDT switch for 12VDC input.? And, I've installed 40mm fan on the back to keep the heat sync cool.? Should have no impact on mic audio at all.
Earlier I was getting 3 mV at the mic element.? Suspect bad meter... so, I put a different meter and I'm getting 30 mV.? Just for grins I checked the other pins on the mic... I'm getting 5VDC to the ring (PTT).? I also checked for AC just in case... no AC on any of the mic pins.
