I would just change the power tube and see if it works.
If so, then I would investigate perhaps replacing power tubes if they are getting weak. Arc-over failure is a common failure mode of weak power tubes.
If the amp does *not* work I would get the amp serviced. So you can approach this in a simple yes/no manner.
If so, then I would investigate perhaps replacing power tubes if they are getting weak. Arc-over failure is a common failure mode of weak power tubes.
If the amp does *not* work I would get the amp serviced. So you can approach this in a simple yes/no manner.