Troybuilt 7800 generator 220V not working

This generator runs a 110V grinder great, but not the 220V stuff. First I tried to run the 3hp radial arm saw, then a 220V air compressor. It wouldn't run either. My son has a Troybuilt 5500. It started to take the load of the radial arm saw, but tripped the power switch. It ran the compressor fine. I tested the voltage, the 220 outlet has 108V at one leg and 7V at the other leg. Same with the two 110V outlets. One outlet is 108V, the other is 7V. I can't find a manual, or any troubleshooting for this problem. I'm thinking it's not the alternator itself, but wires or switches carrying the power. Not sure how to get to the back side of the switches. Any help would be appreciated.