Chosen Solution
I have a velodyne ct150 subwoofer. I have power and the amp is working. I plug the rca jack in half way I get a loud hum that can be controlled by the gun knob. Once the rca jack is fully set I get no sound at all.
@sturg appears to be that something is grounding out. You need to let us know what you connect with the RCA plug and where you plug it into. Next post some images of your boards to see if this is possibly related to shortened capacitors. Use this guide Adding images to an existing question for that. This will allow us to see what you see.
