Man do yourself a favor now pull your ground off and sand where your grounding it to till its clean!!!!! Then before you reattach your ground put a little dylectric grease over the spot where your grounding it to, screw the ground wire back down.

After thats done use a little denatured alchole or rubing alchol, clean the dylectric grease off thats exposed. Then shoot a little pant over it so it wont rust again. Too many times there been crappy grounds in this forum. If your gonna do somthing do it right the first time and don't continue to come back to it over and over and over. If ya don't do this you'll get static and your amp will cut in and out till finally somthing get F******. And yes also check your gains. Oh ya good place for a ground though.