CR-2040 no sound, loud popping, and overload

A few weeks ago when I turned on my CR-2040, there was no sound. Adjusting the volume had no effect, but when I adjusted the balance I would get some loud pops and the overload indicator would come on briefly. I just replaced all the lamps, but the problem occurred before that, when most of the lamps were burned out. I've been unable to locate a repair shop in the Denver area, so am willing to tackle it myself if anyone has suggestions on where to start.

Call Dr. Dan. He lives in Littleton. I take most of my components to him for the complicated repairs. If he can't fix, no one can. Great guy. He won't charge an arm and leg. PM me and I will send you his phone number.