I have a Denon 545R which powers up and display screen operates but there is no sound from speakers. I have connected headphones and at full volume I get a quiet output from tuner section or from an ipod connected in via "tape in". I've owned this from new and has been problem free till now. I suspect there might have been a power surge, electrical spike from a storm but have looked over the internal circuit boards and cant see anything obvious burnt/discolored. I have the service manual but need to some help on where to look in problem solving. Grateful for any help.