Automatic Needle Threader Does Not Work Correctly - Brother NV4000D Service Manual

Failure Investigation for Electronic Parts Automatic needle threader does not work correctly
Is the resistance of the SS PCB
assembly and thread PCB assembly
switch normal?
Resistance of each switch
When switch is pressed : 0 Ω
When switch is released : ∞
Are the main PCB assembly (CN2)
and TH initial sensor PCB assembly
correctly connected?
When the slit section of the TH 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 assembly (CN2)
change between 0 - 3.3 V DC?
Are the main PCB assembly and TG
switch assembly correctly connected?
Is the TG switch assembly resistance
normal?
When switch is pressed : 1 Ω or less
When switch is released : ∞
Abnormal automatic
threading
Y
Y
Y
Y
Y
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Adjust the SS PCB assembly
and thread PCB assembly,
or
N
replace the SS PCB assembly,
or
replace the thread PCB assembly.
N
Replace the main motor
N
Replace the TH initial sensor
PCB assembly.
N
Replace the main motor
N
Replace the TG switch assembly.
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