I do not know how to test whether I am getting power to the main board. I am brand new at this, but if you tell me what to test I will report the results. See also the results I just reported to Barry.
There’s no evidence of a short from solder crossing the +9v and ground lugs on the mains jack. Your assumption is correct that the +9v mains jack wire connects first to the left +9v pad on the 3PDT board, then jumpers to the main board from the right +9v pad. The ground connects first to the top left ground pad, then jumpers to the main board.
Thanks again for taking the time to help. If you could tell me how to test whether there is power on the 3PDT and main boards, I will report my results.