The KA-51A is the slaving control that was originally part of the KCS-55A compass system. It has since been replaced by the KA-51B, mainly due to durability problems with the faceplate mounting holes. Since introduction of the KA-51B, Bendix/King has ceased production of replacement parts for the KA-51A, thus making it virtually unrepairable.

Please note that the KA-51B is not a direct replacement for the KA-51A, but is an easily performed upgrade that only requires replacement of the connectors.