[font=trebuchet ms]OK, your output tubes are cathode-biased, or 'self-biased'. So as long as none of the components have failed, it won't need any adjustment.

The bad news is that you will need to have a tech check it out. Whether that's a factory-recognised shop, or a friend-of-a-friend is up to you. I would first call a dealer to see if it might still be under warranty. If not, you have some tough decisions to make. Whatever you do, you should probably stop using it until you get it fixed. This kind of problem does not get better on it's own.[/font]