Hey there, I'm having trouble with my amp as of recently, it has been acting up a lot within the past month in the way of extremely loud popping and crackling noises even with no volume. It is a 1968 Fender Bassman head paired to a 2x12 4 ohm cabinet and I've been able to play on it just fine until very recently as I stated. I would rather prefer to try and get advice before bringing it in to the repair technician that I go to for a servicing/diagnosis. I have checked and replaced all pre amp and power tubes and they are all fully functioning and every socket is cleaned out. I have sprayed the controls as well to clean them off from any debris or gunk that might have built up. It also pops extremely loudly when tapping the top of the wooden chassis that the amplifier frame is connected to. Sometimes it runs smoothly, and others it's like a wild horse, the noises are extremely harsh and extremely loud and I fear that it might cause damage to the amp itself or cabinet if I don't figure something out. I also feel like the idle static noise you get from vintage amplifiers is a bit louder than usual as well. Sorry for the long explanation but I wanted to be as detailed as possible. Thanks, - Bryan.