I've had this amp for quite a while now. I got it from a friend and when it was given to me the preamp wasn't working. Everything else works fine. I haven't taken it apart yet but was told that the face can be remotely mounted??? Anyway after removing the two screws underneath the front it doesnt wanna come off and I don't wanna pull it. Is this a common problem with these? I'm aware it could just be a bad switch but that brings me back to not being able to get the face off. Any Ideas? Also, are there any other common problems I should be expecting with this amp? Help!