I have a Mesa Bass 400 That I have had for some time now (1985?), actually posted here that is was a 400+ a couple of times but it is older than that. Took a peak at it today and there is no + sign. Anywho....I have not used this in quite some time so I am describing the problem from my faded memory. Basically what would happen is, when playing and maybe pushing the amp a bit, the power tubes would glow very bright, and the fuse would blow. It would only happen when playing out, at stage volume. Not overdriving the amp, not clipping the amp. Just a moderate stage volume, the tubes would glow and out goes the sound. This would happen with either input. Some more facts, This happen in my formidable years, didn't know much back then. We just kinda plugged in and played, It was the simple years. 1985-1986 no interweb thingy. No Bass Player Magazine. No older, more experienced bass mentors just yet. This amp was only over one year old when this problem started to happen. I remember this because it was like two month out of warranty. We didn't play out a lot back then, but we did rehears a lot, so there really was not a lot of hours played through this amp or any road abuse. Always handled it myself and it was always racked. Always used the 2X15 Boogie cab that I got with this amp. Any clue what would cause this? Could it have been something I have inadvertently done (settings)? Was there any common problems with the Bass 400 back then? I plan on bringing this thing to a pro and have it check out, but would like your input. I don't think I can re-produce the problem unless it will be played at stage volume for sometime. I have had this amp for about twenty years and only played it for a year or so. It is in brand new conditions, so I would like to have it fixed, after having it fixed it may be for sale. Maybe not, I'm torn with what to do with it. Thanks, Matt.