I do a lot of work with valve amps, but its hard to know whats going on with those cut wires without seeing the amp in the flesh.

As Marty said, the electrolytic caps can dry out and cause all kinds of issues. The coupling caps in the signal path can also cause a lot of issues if they become leaky, putting several hundred volts into the grid pins of the next stage, which is never a good thing!! I had that issue on an old 1962 Moody guitar amp i fixed recently.

I'm guessing the octal socket i can see at the top of the pic is the socket for the 6V6??