I've had a Yamaha 502 receiver for a little over a year (bought it used). DVD player, cassette deck, VCR, and 4 speakers connected. Speakers are connected with banana plugs. Up until last week, I never had a problem. But my receiver has been turning itself off whenever I turn the volume up. I can only turn it up just slightly above the lowest setting before it does this. This happened with an old Denon receiver I had, but only after using it for 10 years. The Denon never powered back up once it shut down. But the Yamaha comes back on when I hit the power switch. Is this the result of a power drain, and if so, why has this just started happening? Thanks!