In your picture ... if you look in the upper left there is a blue capacitor with a fuse next to it in a set of clips ... the fuse pops out of those clips. In the glass window you will see a wire going from on end to the other if it’s good. If that wire is broken it’s bad. You need to replace it with the same kind of fuse (look for writing on the metal ends). Note each fuse is probably close to a similar looking capacitor. You’ll find 4 fuses on the side boards and 2 on that front board

If no fuses are bad then it’s beyond your know how to fix ...
any competent repair guy should be able to fix this amp