My son did a small soldering project after school and I'm trying to figure out how to help him troubleshoot it.

I took an electronics class about 20 years ago but since then I haven't done anything beyond fixing a lose wire on some headphones. I don't see anything that is obviously shorted and the part that seems strange to me is that the lights on the board that the battery is attached to do not work but the lights on the board that is jumpered do work.

Any advice on troubleshooting, tools required, etc would be appreciated. He wants to do a lot more of these so I need to figure out how to tell what's going wrong.

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