Because I was a little unhappy with the perloid pickguard of my new Burns Bison, I ordered a black one from Mr. Gibson in London and changed them. The Guitar looked so much better to me - and didn't work! No sound, just some noise and a very thin tone! What happened? One of the members in the german music forum noticed, that there was no ground wiring (don't know, if this the correct word in English) between poti and switch. So I found out the reason: The perloid pickguard was pasted with one piece of aluminum foil, but the new one with two overlapping pieces of foil that were not electrically connected! So I put a little piece of aluminum foil unter the screws and the problem was fixed finally.