Thank you very much! This is a good start point
Don't worry about my skill with solder and electronics.. I'm pretty able with that and I hope I will not have problems..

Hi! :) I had to replace the gain trimmer on my MS275 because it is too old (I have the gray version of that amplifier, 1990) and sometimes, specially after a road pit, I got noise and rustle until I move it. I tried to unscrew mosfets and four screw on the board but it seems to don't move.. Someone ...