Power fault can anyone tell me what this fuse does please.
It protects from power surges (faults). That's a typical Switched-mode Power Supply with the usual attendant faults - possible shorted bridge rectifier, dud capacitors, shorted switching transistor, blow controller chip etc.
Try Googling the make/model and the words 'repair kit' as these boards usually have well known issues that some suppliers sell a kit of parts to fix all the common issues.