I'm wondering if someone can help me with my vintage 65 super reverb. First it has been serviced and has all problem caps changed,new jj tubes installed.It sounds fabulous but after playing for an hour or so it starts to distort especially when you pluck the lower strings,it will cut in and out. The sound is sort of like an extreme distortion pedal. I've had it on the bench and tried to create the problem with a chop stick,but all seems good, anybody got any ideas as to what might be breaking down? This is my favorite amp!! Thanks for any help