Well Stan, I seperated the top and bottom boards and found no evidence of any problems in the battery connector area.
I did find a suspicious component on the bottom of the lower board. ( see photo ). I soldered a new one from a donor board . The wire going across the suspicious area was rubbed through the insulation but only enough to barely show a glint of shiny wire. Don't know if there was any connection with the component in question.
Anyway nothing changed with the original operation ............however ....... I think the boards are toast. 🤔 I must have touched some wires together that must have caused a problem. Something I have never seen on my other proto 2 /3volt engines wiring.
The red and black wires from the trucks , the two entwined speaker wires and the yellow and white entwined wires to the motors all had about five mm lengthwise open slits in different places on the insulation ,down to bare wires. I must have touched them together when putting the boards and connectors back together.
Anyway before putting the shell back on ,I ran it on DCS this time . I had forward and reverse lights , no sound and using the remote at 1 or 2 SMPH the engine would start out slow and gain speed, probably to 100 SMPH !😨. I was able to do startup and shutdown intermittently only.
So I suppose there isn't much use in further work without getting into a very large cash outlay ! 😕
Gotta thank you for your input Stan. 🤗