I have the same unit. It is rather cheaply built but is still working well after almost 30 years with no actual repair. The switches are not the best and they will become intermittent. If you have this connected via the tape monitor loop, try running the system without the equalizer and see if the problem disappears. In my case, it has not been pops but rather intermittent cut outs. Activating all of the push button switches a few times will clear the problem.