I know this is a bass forum, but figured you guys would know the answer. Our guitarist is playing through his Fender Blues DeVille amp and it just quits. One can now only hear the faint sound of guitar when he plays. Is it a 99% probability that he has just blown a power tube? The amp has two 6L6 power tubes and three 12AX7 pre-amp tubes. Any way to tell which side the problem is on? If we had blown a pre-amp tube I'm assuming sound would still come out? I'm thinking of just calling Mesa Boogie and having them send me five new high quality tubes - and just looking at this as a good excuse to upgrade the sound/amp. Any advice appreciated!