I have a 5150 that I'm having issues with. One practice it suddenly went dead silent (but the pilot light still lights up). I switched the fuse, but to no avail. I read somewhere that sometimes rust in the fx loop can mess things up, so i plugged a short cable between the in and out of the loop but that didn't work either. I've tried different speakers and speaker cables, and the guitar is fine etc. I've never switched tubes before, so I'm guessing I might need to do that now? Just want to check if there's something else I should check before I do that. Hope someone can lend me a hand!