I have a Onkyo TX-VR940 stereo receiver. Im having issues with the receiver's volume that comes out of it. I can turn it on and it'll work fine for a while and then it seems like after it is on and it warms up a little that it starts by either the left or right speakers will fade out. Then it sometimes comes back on by itself. But if I turn it off and on it comes back on again. I have a Sony Stereo receiver that does the same thing... Any thoughts?