Pulled the chassis on my bandmate's Fender Keyboard 200 to clean the pots and when I put it back in, I am getting a loud buzzing (120Hz) sound. There are 3 sets of speaker wires (12" woofer, 10", and tweeter) that I reconnected after I tried cleaning the pots. Fired it up and noticed the loud buzz. When I hold the black/white pair that goes to the bottom speaker, the hum completely disappears. As soon as I let go, it comes back. I am wearing shoes so I am not acting as a ground. Cleaned all of the jacks in case there was in issue there with no luck. Any ideas?