[Milsurplus] more chopper information

[Ray Fantini]

More chopper fun! The choppers in the 618S1, ARC-38 and 38A are all Collins 354-1021-00 they also have an Airpax 300 part number on them. The 180L automatic antenna tuners use a larger chopper Collins 354-1014-00 or Oak NC600 All appear to be 6 volt 400 cycle  seven pin base and all have the same internal alignment of the pins, coil pins 3 and 4 ground and shield pins 2and 5 contacts pins 1 and 6 and arm on pin 7. Interesting that the chopper in the 180L dose double duty. The arm is grounded and one contact interrupts the feed to the loading servo and the other contact interrupts the feed to the phase servo so two different amplifiers only need one chopper, once again those guys in the fifties were good.
Ray Fantini KA3EKH