Have you checked the plastic cup that holds the 3DC3 socket? The HV seems to burn through these pretty easily, arcing to the chassis. A coat of GE silicone II on both the inner and outer surfaces fixes it right up. As you can see from the picture, the burn holes are practically microscopic. I've found at least three zenith sets in basements with the same arcing problem. I have a feeling thats why the sets are retired, they started snapping and the owners didn't bother servicing them.