It sounds as if the input has either worn or the contacts have become spread apart so far and the jackplug cannot touch them. If you buy a new input I'm sure you could find a local electrician or PC shop that would solder it back on for you. It's a simple case of removing the input which would mean taking the front control panel off. If it's too complicated for you try and find a guitarist that knows about these things, it's pretty simple really.
Ken Rowlands, January 2009
