Brother Innov-is NV4000D, Service Manual

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Electronic Parts
Failure Investigation for Electronic Parts Pulse motors do not return to starting point
Replace the initial sensor
PCB assembly.
When the slit section of each initial
sensor 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
assemblies (CN2, CN3, and CN25)
change between 0 - 3.3 V DC?
Replace the TG switch
assembly.
Is the resistance of the TG switch
assembly normal?
When switch is pressed : 1
Ω
or less
When switch is released : ∞
Are the main PCB and TH, PF, and
AT initial sensor PCB assemblies
correctly connected?
N
N
Replace the main motor
N
Are the main PCB and TG switch
assembly correctly connected?
Replace the main motor
N
Y
Y
Y
Y
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When the power is turned ON, the pulse motors do not return to the
starting point.
When needle is up : Z pulse motor returns to its original position.
When needle is down : F and S pulse motors return to their original position.
Regardless of needle position, AT, TH, PF, TG, and C pulse motors return to their
original position.