Hello I need some help with a valve head that I bought 2nd hand recently (laney vh100R) All was going well with my new acquisition, until the other night when after warming up the gear, I fired my guitar in got about 10 minutes play, then "crackle"....no sound anymore. All the tubes are still lighting up and all the LED's at the front are on. Anyone know whats up with it? I suspect its one of the valves, but if that's the case why are they all still glowing? I have never owned or really even played a valve amp before this, so don't really have a clue, if it is in fact a valve then that's no bother, ive got my debit card ready to get some new ones. Can someone please point me in the right direction on this one, as google has been as useful to me as a fish with tits.