Amplifier, Denon, not working (Meole Brace SY3)

This is a Denon PMA-355UK integrated amplifier, a bit scruffy and a small hole knocked in one side at some time in the distant past. It has been working fine until a few days ago. The headphone socket still works OK, and a subwoofer plugged into the preamp output still worked so I assume it is the power amplifier stage that has gone. It may be as simple as a blown internal fuse or something more serious, but I do not want to spend time looking as it would only then stand in a cupboard. Anyone who wants to play about might get it working, or just use it as a preamplifier or headphone amp.