I’ve started to clean up and identify the parts that are bad or damaged. Not only was the Molex J5 on the A10 board melted, but also the far end connector J2 on the A14 board in a compartment in the back of the generator. I was lucky that the ground return wire did not damage adjacent wires in the bundle. Here is a simplified schematic of the unregulated portion of the +5 volt logic supply detailing the parts that were damaged.
Here is the HP 8656A pulled apart so that the molex connectors and ground wire can be replaced.
This picture shows one of the Molex shells after repair. Note that Pin one had to be replaced with a non-HP pin.
New ground return wire is back in place and the wire harness is all bundled back together.
