I bought a quad 77 pre amp via Ebay. the seller states that it is a 115v model and that modification is needed. In the quad 66 series changing two bridges on the motherboard did the trick (service manual needed!) is this the same in the 77 series? in the 99 series the only adjustment is a different fuse. any comments on this? anyone with the original manual or rather a service manual???? thanks in advance