Hey guys

First time posting any help would be much appreciated. I recently traded for a Weldanpower 250 ac/dc with a Perkins diesel that had no output. I've tried to run through and check the things I know right off the top of my head but now I'm stumped. The engine runs great and will auto idle.

1. Verified I have 5.0 ohms across the slip rings with the brushes removed.
2. I have 12v to R3 and around 4.5v after R3 and at the brushes. it does raise to around 6.0 volts when the engine is on high.
3. I have checked continuity across leads 4 and 5 at D2.
4. I have checked R4 and it does have around 10 ohms when on .

I have tired to flash across the brushes with 12v for about 5 seconds, but it still will not generate power and I'm not sure if i am missing something. I'd appreciate any advise.