Problem with Adcom ACE 515

My Adcom has recently stopped shutting off the amplifiers when I power down my system. Everything else works exactly how it is supposed to. Is this a common problem with old 515's? Can I fix it? Should I replace it? Should I upgrade? My system has grown and I was thinking about buying another one but this may be the sign to get a larger line conditioner. I also have a small budget so I would need to stay around the $200 mark used. Any suggestions?