The fuse is located close to where the red battery wire is soldered to the PCB.

As far as I can make out it is a 2.5A rated fuse (marked with an O). Sadly it is not possible to detect the speed rating of the fuse.

With an Ohms meter probe the fuse i.e. check if there is continuity from one side to the other. If the fuse is OK there will be almost 0 Ohms across it. If the fuse is blown it will show open circuit i.e. infinite resistance.