@dmac61 measure the voltages on the connector for the main board cable. Measure on the power supply side. The voltages should be stenciled on the power supply. If all of those are present the issue will not be your power supply but most likely your main board. It always helps if we can see what you see. For that purpose, post some good pictures of your boards with your QUESTION. [guide|21499|Adding images to an existing question - iFixit Repair Guide|new_window=true]