If there is no fuse externally, it is possible there is one inside. More likely than not, the amp went bad though, and highly likely it is capacitors not a fuse. IMO, should be under warranty, so I'd contact JBL. Budget sub amp failures are quite common. There's a big difference between passive speakers - which you should not need a warranty for, and a powered sub is that amp and the amp is by far the most likely thing to go.