Brother BAS-343E Instruction Manual page 58

Error codes (Bobbin changer)
If an operation problem occurs, a buzzer will sound and an error code will appear on the display screen.
Code
E.71 If the sensor on the underside of the bobbin
cassette does not activate when the bobbin
changer is rotated:
1. The changer motor does not operate correctly.
2. The sensor does not operate correctly.
E.72 There is no space in the bobbin cassette when
the rotary hook bobbin tries to return to the
bobbin cassette.
The sensor does not turn on or off when it should.
E.73 The sensor which detects the raised cylinder arm
does not turn on when the arm is raised.
The sensor which detects the lowered cylinder
arm does not turn on when the arm is lowered.
E.74 The bobbin is already in the changer at the
bobbin retract position.
Cause
BAS-343E
Remedy
1.Check the changer motor and the wires connected
to the motor.
2. Check the sensor at the back of the cassette
and the wires connected to the sensor.
Make enough space in the bobbin cassette.
Check whether the tab might be holding the bobbin
and causing the problem.
Check the cylinder sensor for detecting the raised
cylinder arm and the wires connected to the sensor.
Check the cylinder sensor for detecting the lowered
arm cylinder and the wires connected to the sensor.
Check that the bobbin is in the rotary hook rather
than in the changer at the sewing start.
12. Error codes
51