Upper Thread Sensor Does Not Work Normally - Brother NV4000D Service Manual

Failure Investigation for Electronic Parts Upper thread sensor does not work normally
5 - 24
Upper thread sensor does not
work normally
Are the main PCB assembly and
upper thread PCB assembly
correctly connected?
Y
When the slit section of the upper
thread PCB assembly is switched
to the open / closed position with
the power on, does the voltage
between pins 2 and 3 on the main
PCB assembly (CN24) change
between 0 - 3.3 V DC?
Y
Replace main PCB assy.
Reconnect the main PCB
N
assembly and upper thread
PCB assembly.
N
Replace the up thread PCB
assy.