Engine Gravely 810 Wont Charge Battery

[jbstrawb]

I have a 70's vintage 810 riding mower that runs great once you get it started. It seems the battery is no longer being charged as it is running. I replaced the battery several times and I can jump start it without a problem. Looking at an electrical diagram of the 810, its seems that the regulator/rectifier may be the problem. Does anyone have any advise on this problem? Thanks in advance.

 

[jbstrawb]

I got a new battery and things seem to be doing fine now. What should be the voltage on the battery if the regulator is charging properly? I measured between 12.8 and 13 volts while it was running.