Raymarine Autohelm ST6000, Service Manual

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Autohelm
Autohelm Autohelm
Autohelm
SeaTalk Service Manual 4
2.2. Reverse Connection Protection
TR1 and TR2 along with RL1,2 and 3 ensure that external misconnection of Heavy
duty V+, Heavy duty 0V and M1 and M2 will not damage the unit.
2.3. Bridge Amplifier
TR6, 7,8 and 9 form a bridge amplifier to control the actuator motor. Four modes of
operation are possible, each selectable with a binary code on drive A and drive B.
Mode 1 - Drive A and drive B both a logic 1. The motor is shorted via TR7 and TR9.
This mode is used for stopping the motor quickly.
Mode 2 - Drive A and drive B both at logic 0. The motor is open circuit and therefore
may run as a generator allowing measurement of motor back emf. R14 and R16 in
combination with R25 and R28 on the computer PCB scale down the back emf.
Mode 3 - Drive A is at logic 1. Drive B is at logic 0. The motor will rotate clockwise.
Mode 4 - Drive B is at logic 1, drive A at logic 0. The motor will rotate anti-clockwise.
TR4 and TR10 are interlocks, switching off TR8 and TR6 when both drives are
switched high in mode 1. C3 and C20 suppress motor brush noise.