I did that on module #6. I probably tightened it about one full turn of the nut and hooked it back up. Still hummed. So, I tightened it a bit more. Maybe another couple of turns. I still have yet to try it again, but I'll do that real soon after I wake up a bit more and feed the pooch (already took her for a walk). With two modules out, I can now get access to the bolt and nut while it's powered by putting the noisy amp in slot number 7. If it still hums, I'm going to try loosening it up a bunch. Mine were more than hand tightened, I think (but my hands are weak, so I'm a poor judge).