SVT Classic through (2) 1x15 cabs, 4 ohm load. The head is USA made (if that matters) from around 2008. I've never had any other issues with it. Last night, we split a gig with another band. We did a set, they did a set, then we finished off the night. Amp worked great for our first set. I let the other guy use the amp and it was fine. Last set, and I notice the fan is pushing a lot of heat out the front before we start. Maybe it was normal, and I never noticed that before. First song, and the amp cuts out and goes into protect mode... flashing green/red led's. No pop/bang, or smoke. I always carry a backup, so I switched to that. This morning, the amp appears to be fine. I was prepared to test tubes due to the lack of any kind of smokey smell, etc. This has never overheated on me before. But I guess it was powered up for over 5 hours. Any thoughts on what may have happened, or what I should be checking? Thanks.