Reddit reviews Fender Champion 600 Tube Set, JJ Tubes (x1 6V6, x1 12AX7)
We found 1 Reddit comments about Fender Champion 600 Tube Set, JJ Tubes (x1 6V6, x1 12AX7). Here are the top ones, ranked by their Reddit score.
Being that you've got nothing to compare it with, your best shot is to buy a new power tube (which isn't that expensive, typically), of which I'd recommend a Tung-Sol 6V6GT for the Fender Champion, and toss that in. Unfortunately, you can't compare your tube to another one in the amp because it's just the one, so your best shot is just to retube.
From what you've described, it sounds like a dead power tube. It happens after a while in every amp; tubes die. If it was a pre, you'd still be getting output but it'd sound weak/muddy/off. Feel free to replace that one too if you want, as it might die soon as well. Here's a link to a retube kit.
Hope your amp gets back in action soon!