PPRuNe Forums - Patriot/Advent power problem

Hi chaps - a friend has brought me his patriot 2006 which I believe are made by advent. It has a power issue. He's been running it on mains for the last 4 years since purchased new but with the battery installed. Now its developed a fault. When on battery he gets no response from the unit at all and I wouldn't be surprised if the battery is now completely dead. On mains, the adaptor green light comes on and the "charging?" or "mains" light comes on but when you press the "power" button you hear a very quiet click and the "mains" light extinguishes. The light on the power adaptor remains on throughout.

Would anyone have any idea as to what the issue may be and if its going to be an easy/expensive fix at all?

As ever, all help muchly appreciated.

Fowler