430w comm -no sidetone
 

Hey Kevin, did you ever figure out your problem? I have the identical situation after a full year of flying with no problem. Haven't looked at power inputs yet, so maybe?? So far, depending on Com 1 for communications.

I'm still having a hard time believing the apparent cause (excessive resistance in power connection), but the problem went away when I reseated the power wires where they connected to my fuse block. Perhaps there was a bit of corrosion, creating an excessive voltage drop when the current was high, i.e. during transmission.

The problem reoccured about a year later, and this time I gave the female spade connector on the end of a power wires a bit of a squeeze with pliers after I pulled them off, to put more pressure on the connection. This fixed the problem, and it has not reoccured since.

If cleaning and reseating all connections in the power wires doesn't do it, try the same thing with the grounds.

Good luck.

Tx problem with PMA8000
 

I had resently TX failure through audio panel in fail safe mode and normal mode measuring resistance through pins of audio panel passing test
but mike signal was not passing and people could hear some scratchi noise when you transmit checking signal with oscilloscope revialed the issue

lowpass filter capacitor went dead dispite they claim on there website that it never fails to avoid this problem happening n the future replaced it with jumper