Tonight, after playing for about 15 minutes at low volume my sweet '64 B-15N made a fairly loud click and completely lost volume, nothing left but a buzz. While checking to make sure the cords were ok I noticed a faint wiff of something burning. Oh crap. The power tubes were so hot that I felt the heat coming through the tube cage. So I turned it off and took off the cage and realized that everything was too hot to touch. This amp has been trouble-free for about 15 years when the transformer blew. It's probably been that long since I changed the tubes too but I don't play it much, maybe an hour a week. Does this sound like a transformer problem? tubes? Something else? Any help appreciated. Thanks.