This amp has let me down during a gig a number of times. It's been to a tech and he can't find anything wrong with it. It's speaker lead input related. During the gig during a song it cut out, I went back to the back of the amp wiggled the speaker lead and it came back on for a bit and off. This happened several times. The next time it happened I had another newish speaker cable and plugged that in and it worked for awhile and cut out. Here's what I think after reading about another post with the same problem. The Cliff Jack does not have UK on it and according to a poster it should have. The other thing I noticed when I touched the speaker lead plug was that it had a sizzling vibration to it???? NOW - At our practice shed I usually have a Buggera valve amp on the Marshall box and the Marshall head sits on the Buggera head. During the gig the Marshall head was sitting on the Quad box. Could it just be vibration or does the amp go into some sort of occilating space and just dies???? I know that sounds corny. If I replace the Cliff Jacks with something better I think that MIGHT solve the problem but with so much crap out now how do you really know?? This problem has been with this amp for about 9yrs now with two techs not able to fault it and yet it occasionally drops out. I can't get past the Marshall sound and probably don't really want to. Even the Bugera sounds a bit sad next to it. Any ideas please???