52-13-01 COLLINS RADIO: Applies to All Models 51R-1 and 51R-2 Radio Receivers.
Compliance required by November 1, 1952.
To eliminate failures of 90/150 cycle tone localizer filters due to electrodeposition of copper from the coil windings to the laminated iron core, modify the receiver in accordance with Collins 51R-1 and -2 Service Bulletin No. 21, dated May 7, 1952, by removing the B plus voltage from the 90 and 150 cycle filter input circuits.