JL Audio 500/1No audio out unless I ground the output RCAs.

Hi, working on a JL Audio 500/1 amp. All the switches needed cleaning. Amp runs but I have no audio unless I ground the output RCAs. Not the input RCAs. If I ground the output RCAs, the amp runs normal. Any help would be appreciated. Thanks.
 
I don't know what happened. It all of a sudden started playing. Guess I'm dealing with a bad connection or something. I have two power supplies. I tried it on both and I have output. I'm gonna run it and wiggle some things around. See if I can get it to go back out.
 
I have a 500/1 slash .with an input issue if rca wires are hooked up and amp is on the subs start to play a tone that gets louder and louder the longer rca’s are connected .so I unplug them no tone plays .so I tested to input terminals and they have no continuity between them on the ground and no conitinuity from either term to main board ground .amp turns on fine no protect or low ohm .changed rca’s still does it.i hook up a diff amp no issue so I know it’s not the so I know it’s not the source or rca’s .just want a few ideas before I open her up