I bought a refurbished Marantz SR4300 about a month ago and it is great except for one problem, it won't stay on. I'm thinking it is a heat safety mode that cuts power and puts the unit into standby. If I have the unit on for a period of time, if will just go into standby and I can't turn it back on, it has to be unplugged. Does anybody have experience with Marantz receivers and is this a feature or a concern? The cabinet I have it in isn't the most ideal thing for heat but it is going to have to do for a few more weeks.