Mep804a charging issue

I have an 804a from gov planet with three hours after it’s factory reset/reman. It will generate if I hold the switch in start mode but loses it after it’s released. Tested the magnetic pickup and is just out of the parameters in the troubleshooting. Looked at the voltage regulator and it’s $20 time delay fuse was blown. Replaced and it’s blown again immediately . Any leads to where I should look next? Or know a tech in South Dakota knowledgeable on these units?