Kubota B21TLB (B21, TL421, BT751) Toyota SDK4, T116 Bobcat
I don't but there is general alternator info in this "All kubota tractor workshop manual" www.kubota.cz/data/manualy/all-tractors-wsm-en.pdf
General alternators need battery power to main(large) terminal, and fused power to regulator via dash lamp for excitation. If your dash lamp doesn't glow when key turned on, check lamp and fuses as this is part of the excitation circuit.