Yamaha EF4500iSE Theory & Diagnostics Manual page 47

And last, test the Exciter Armature Coil resistance
and short to ground.
Then the Main Field Coil resistance and short to
ground.
If the problem was not with any of these compo-
nents, it will then be necessary to replace the AVR
circuit board.
Correctly following these procedures, should have
revealed the problem in one of these areas.
ExCITER ARMATURE COIL
RESISTANCE TEST
SHORT TO GROUND TEST
MAIN FIELD COIL RESISTANCE TEST
SHORT TO GROUND TEST
2-13
Generator Diagnostics