Thread Breakage Detection Does Not Function Normally - Brother PR655 Service Manual

Failure Investigation for Electronic Parts
Thread breakage detection does
not function normally.
Is the FFC for the thread quantity sensors
properly connected to each thread quantity
sensor and connectors (CN1 - CN6) on the head
PCB? Is the orientation of the FFC correct?
Is the head lead properly connected to
connector CN7 on the head PCB and
connector CN9 on the main PCB?
Is the resistance between each terminal at both
ends 1 or below when the TH (thread quantity)
sensor's FFC is removed from the PCB?
Is the resistance between each pin at both ends
1 or below when connectors at both ends of
the head leads are removed from the PCB?
Does the machine function normally
when the TH (thread quantity) sensor
PCB is replaced with a reliable one?
Does
normally when the head PCB is
replaced with a reliable one?

Thread breakage detection does not function normally.

Y
Y
Y
Y
N
the machine function
Y
Change the head PCB.
5 - 9
N
Connect it properly.
N
Connect it properly.
N
Change the TH (thread
quantity) sensor's FFC.
N
Change the lead wire assy:head.
Y
Change the TH (thread
quantity) sensor PCB.
N
Change the main PCB.