This is a 1989 JCM 800 2210. It is starting to Squeal, Fart, Pop and Crackle when set up as it always has been over the last 20 years. My trouble shooting consisted of changing out Power tubes and biased to 70% disipation in addition to 5 new Pre-amp tubes. Different Guitars/Cabs/Cables. On-Board Reverb on off. The problem persists, "Until I turn down the Gain Knob below 7.5 or less. In addition the tone goes to hell at this low level and sounds even worse at higher settings. When turning the Gain up above 7.5 it has a modulation/phase type effect to the gain structure in addition to sounding as if it is about to blow and must be shut down/backed off immediately. I have owned many of the 2210/2205 models and have always ran them on the boost side with the Volume and Gain maxed at 10 then adjust the over all volume with the master volume or Input/Output controls of a processer in the loop. I assumed that with all of the talent here at the forum one or all of the Technical Genius's would be able to point a finger in the right direction if not just out right say, yeah it is x,y and or z. Thank you in advance. David Hopkins.