I recently pick'd up a used SWR SM-400 head at my local. Brought it oot to jam TWICE, and the darn thing frig'd oot on me. FYI, I am running the aforemention'd head, bridge'd to 400w, into a Peavy 4x10 cab. There is no power rating on the cab, but it seems pretty robust. The first time it happend, I was playing at a high, but by no means crank'd volume, when the amp just stop'd making any noise. No loud bang or pop. Just silence. Not even white noise from the cab. It was still clearly power'd on, however. I DID try testing it by touching the core of my cable, and multiple other cables that I tried in both inputs. Nothing. No response. I cross-check'd the cab by plugging the amp into a buddie's cab with a different cable. Nothing. The amp was definately the souce of the problem SO, a couple of days later, I broke'er oot again, thinking that MAYBE it just overheated, (the thing gets realllll toasty.) It werked for aboot 10 seconds. Then, THIS time I heard a quiet pop sound, (although the amp was turn'd down really low to begin with,) and the two LEDs, (compresser and peak clip limiter, I think,) both lit up steady. I don't THINK it did THAT the first time. However, like the time before, it was dead. Havn't tried it again since. Now, apperiantly it had just been re-tube'd before I bought it, (it's a hybrid, with one preamp tube. The rest is all solid-state.) And I'm pretty amptarded, so I don'even know if this could be a tube related issue. I also know perfectly well that it's probably gonna be making a trip to the shop. However, I'd like to have SOME idea of what happend. Here's the owner's manual, if that helps anyone at all... http://www.swrsound.com/products/ownersmanuals/sm400om.html Thanks for anything that any of you can do.