Lets try just the MEP-806A first.
1. It was missing the quad fuse, and you replaced it.
2. During start up, the gen set made voltage, as long as S1 is in the start position.
3. When you let go of the S1, the quad fuse blew, and the gen set stopped making voltage.
4. Every time you turn the S1 to the start position, you get voltage, but not when S1 is released.
The reason you have a quad fuse in the first place is to protect the exciter winding, should the A1, (Volt Regulator) goes bad in the OVER VOLT mode. When that happens, it can shoot 600 volts into the exciter windings and damage them. So I would say you need to try another A1 in the MEP-806A. Have you read the information that was in the TM section concerning the differences between the TRC and Libby A1? If not, maybe you should. You can not mix parts between the two manufactures.
