When I turn the amp on, the purplish power indicator light doesn't come on, and the tubes are showing no glow whatsoever. The individual green, orange, and red lights that indicate which channel is on DO work, and I can switch channels. There's obviously no sound at all. The fuse "looks" fine, but I'm not sure if you can visually tell if a fuse is good or not. I've checked the power cable and it's connected properly. This amp just started doing this after 4 years. It just so happens that I tried the "EXTREME" mode for the first time last night, so that might have something to do with it. Can anyone tell me what might be causing this, and how I can fix it? I would really appreciate any help. Thanks.