Brother LX-200 Service Manual page 124

Trimming Motor Start Point Detect Circuit
This circuit rotates the trimming cam and Y-cutter cam forward and backward with
the trimming motor (T/C motor) to detect the position of each cam.
The trimming switch (TRG) is designed to turn OFF 150 steps before the trimming
cam standby position (T-cutter top position). Consequently, TRG switch is normally
ON.
The Y-cutter switch (Y-G) is designed to turn OFF at the Y-cutter top position. When
the power is turned on, the circuit checks that the Y-G switch is OFF. If the switch is
ON, the trimming motor reverses until the switch turns OFF. The position of the
TRG switch is not checked at power ON.
Y-CA Motor Drive Circuit
This circuit drives the Y-CA motor using 2-2 phase excitation from the +24V DC
stabilized constant voltage and maintains a low voltage during Y-cutter operation.
The stepping motor excitation phases A, B, C, and D are controlled by main CPU
ports P03, P02, P01, and P00, respectively. The seven transistor arrays
incorporated into QA3 drive the Y-CA motor.
The drive voltage is controlled by the main CPU port P65, which applies +24V DC to
the Y-CA motor through transistors Q3 and Q4.
Fig. 5.5-3 Trimming Motor Start Point Detect Circuit
Fig. 5.5-4 Y-CA Motor Drive Circuit
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