@pip555
Thanks for the measurements, the readings confirm that brown and yellow are 100V windings, red and blue are 120V windings.
You can go ahead to move the jumper wire J1 to J4, J3 to J5. That will change the voltage setting from 100V to 120V.
Accuphase E-370 Mains Voltage setting:
100V Mains = J1 , J2 , J3
120V Mains = J2 , J4 , J5
220V Mains = J1 , J6
240V Mains = J4 , J6