I have a Marshall 8100 and It has run into a few problems. When I turn it up it starts to pop and cracle and then go out. Now it won't even work. What my theory is, Something is lose within the amp, but i don't know how to remedy this problem. If anyone has a diagnosis, please share it. Help is greatly appreciated. PS It isn't the cab, I already checked it out.
ummmm taking a random guess but is it the tubes? like, are they old? or broken?
Blown tube (probably). Don't try to start it anymore, you might end up blowing the power transformer or output transformer, which would triple the cost of repair. Contact Marshall to see what to do about it.