I have an avr635, and

Question

i have an avr635, and recently it's been blacking out. in such that when the volume is slightly higher than usual it will shut itself off, into power save mode that is.I have 2 old sansui sp450 speakers hooked up, still in great shape, and can handle my needs well.any ideas? i've heard possibly, there is a cooling fan inside the 635, and that this could be malfunctioning, if this is the case, how would i know if it's not working?look forward to any help you can [e-mail]