The Radio Information Board

Pin 15 is hooked with a wire to a ground bolt on the seat/frame, and yes the hum does quit when the ignition is off. emtposcar

first, the reason for the pin 15 is one schematic said that if any accessory was utilized using this plug it needed a ground placed in pin 15. Second, if i plug the speaker directly into the 2nd head the speaker does not work at all. emtposcar

I have a dual remote head tk-730 G. I have it installed in an ambulance. My problem is that the rear speaker has a hum to it when the ignition is on. The front head speaker is plugged into the remote head, the back speaker is plugged into the control unit, low to 6, high to 12, ground to 15. Control...