Actually, we do NOT recommend repair of these! The core of the control was of magnetic amplifier design. The magnetic amplifier coils were wound with enameled wire and wrapped in friction tape…not very moisture proof. Over time, the enamel starts to flake off, causing leakage between windings which results in drift of the voltage dead-band, or also one or both of the band edge settings.
We can repair if you want us to, however, we cannot guarantee against this drift.
A better choice is replacement with an SVR, a UCA, or a Beckwith M-0067. The mounting and terminal makeup are identical between these types.