The Main Shaft Does Not Rotate Normally - Brother PR655 Service Manual

Failure Investigation for Electronic Parts
The main shaft does not rotate
normally.
Is the main shaft encoder deformed,
bent, or damaged due to contact?
Is the main shaft sensor's lead properly
connected to CN19 on the main PCB?
Is the main motor's lead properly
connected to the power supply
PCB's lead?
Is the lead which connect the
power supply PCB and the main
motor properly connected to CN4
on the power supply PCB?
Is the lead which connect the power
supply PCB and the main PCB properly
connected to CN27 on the main PCB
and CN3 on the power supply PCB?
Does the machine function normally
when the main shaft sensor PCB is
replaced with a reliable one?

The main shaft does not rotate normally.

Y
Y
Y
Y
Y
N
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N
Change the main shaft encoder.
N
Connect it properly.
N
Connect it properly.
N
Connect it properly.
N
Connect it properly.
Y
Change the main shaft
sensor PCB.