[CA] [CA11] rudder indicatation stuck on hard over, rudder sensor ok

[cgold]

I have a system with an ST6000+ control head, a type 300 computer, a rotary rudder sensor, type 2 linear drive, and flux gate compass. System has been working fine for a number of years. Yesterday, the control head showed hard over to starboard and couldn't be used. Rudder sensor passes the tests for resistance so appears to be ok. Control head seems fine in every other way, good compass headings, calibration procedures working etc. Disconnecting rudder sensor red and green and or switching them has no effect. It's on a seatalk network with sailing instruments and radar etc...Anything else to try? Can the Type 300 be repaired at this point? What computers could replace it without replacing everything else?