Well you learn something new everyday. I was having problems with my '67 AC30 TB with the E & B string notes. They were getting very trebly and breaking up with a warbling type effect( thats the only word I can describe it as), so was told it could be the speakers, could be dry solder joints, could be this, could be that. Anyhow I replaced all the valves (preamp & power) and bingo! the problem was still there.
Rang my mate Phil E and asked who fixes his amps. Gave me the chaps number rang him drove 30 klms to let him have a look at it. I took over the FR Strat , plugged it in for him to have a listen to my problem and low and behold, not a bloody thing went wrong. I felt like the proverbial goose and he smiled at me and said" do you use a fan behind the amp. I said yes and said "well I beleive that is your problem". Wind from the fan apparently breaking up the notes. Brought it back home and Voila! Took away the fan & no warbling. Put the bigger fan I use in front of the amp as I stand infront of the amp and once again the warbling sound took place again . Took away the fan from the front of the amp - no warbling and the sound is back to where it should be.
Bloody idiot!!!
cheers
Buckshot
) either side of the stage - just before going on I went out for a final tune up and couldn't get the guitar in tune - it really was bizarre. After about 5 mins I realised the fan was blowing directly at my guitar affecting the strings !!! turned my back to the fan (which you should never do 
) and hey presto - tuning no problem. 
