Sonics E-Series - Manual (Page 10)

15) Verify that the main transformer is tapped for your incoming line voltage. Move the black wire to the
appropriate tap which is on the transformer label. If your incoming line voltage is 208V, move the black wire to
the 200V tap.
16) Check the tuning coil assembly. Make sure the nut behind the ferrite is tight. Sometimes it becomes loose
and will affect the tuning. Also, check the actual coil itself. In some instances, it will separate from the ferrite
base and will sit in the assembly loosely. If this occurs, reseat it with silicone.