Nice little amplifier with a great sound but is notorious for its cut-out problem. If you crank up the volume the mute light flashes and the sound cuts out.
If you have this problem there is an easy DIY fix (link at the bottom). If you don't feel competent enough to remove the lid than you'll have to take it to a Hi-Fi repairer to get it fixed. Take a look at the attachment in the following link which explains what you need to do. It will also give you some idea if what the repairer is charging you for if you take that option.