Re: 7854 Repair & Restoration

Ed Breya

I just found vertical amp board that was from a 7844 or 7904 - marked 670-2768-02. The driver and output cans are both held by the same type of plastic clamp. The clamps each have two special screws holding them to the board, with a spring at one end for compression. There is a contact in the center of each one, with a lead going to the board (ground?). There is also a sheet metal layer about 0.032" thick added to the component side of the board in this area, apparently to serve as a ground plane and for cooling. So, the compression force is probably essential also for good thermal contact of the cans to the plane. I can't tell if there's any thermal grease underneath. The contacts are definitely not welded to the cans - in fact, the clamps have notches on one end to allow them to swing away for access to the cans without removing the screws.


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