New to me tractor, pulling a 12 row cyclo planter.  I made one pass, then the pto, which is running the pump for the fans, quit.  I had to restart the tractor to get it to engage, it ran for a minute or two and quit again.  shut off and restart tractor, now it will only run about 5 seconds before it kicks out.
     I checked hydraulic level, good there.  Thought maybe electrical, so I cleaned connections on the relay in the fuse panel.  Relay clicks when the switch is turned on, and clicks again when the switch is pushed down, even though the pto has already quit on its own.  The ralay clicks when moved to off or on, but the pto won't attempt to restart unless the tractor is shut off and restarted.  Indicator lights on dash and console go out when pto quits.
     Any one have this propblem before? At this point I'm thinking the problem is inside, possibly pto clutch.