I have one of the old GK 200MB combo amps. The hex nut on the input jack was loose. So I got out a wrench, over tightened it and the threaded receiver broke off. Turns out to be plastic. I took the top plate off the amp and saw that the jack is soldered directly to the circuit board. Not sure if that part is available. I still have the broken off pieces. Do you have "input" how to repair this? Love the amp but it makes an ugly doorstop. Thanks.