Pulse Motors Do Not Return To Starting Point - Brother NV4000D Service Manual

Failure Investigation for Electronic Parts Pulse motors do not return to starting point
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.
Are the main PCB and TH, PF, and
AT initial sensor PCB assemblies
correctly connected?
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?
Are the main PCB and TG switch
assembly correctly connected?
Is the resistance of the TG switch
assembly normal?
When switch is pressed : 1Ω or less
When switch is released :
Y
Y
Y
∞
Y
To next page
N
Replace the main motor
N
Replace the initial sensor
PCB assembly.
N
Replace the main motor
N
Replace the TG switch
assembly.
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