Hi there I am looking at buying an amp (cheapish ,used) it seems I may have a chance to get this amp very cheap but there is a problem with it that the seller describes as "small buzz when playing." they go on to say seems to be an earthing issue and if they tie a wire around a slightly removed case screw and the other end around the earth pin of the plug it stops ......my question is does anyone know if this problem is somtthing pretty simple and easy to fix or cheap to get fixed