Baby Lock BLMY Service Manual page 199

Failure Investigation for Electronic Parts Main motor rotation abnormal
• Main motor rotational variance
• Does not reach maximum speed
• Speed cannot be adjusted
When the speed control lever is
moved with the power ON, does the
voltage between pins 2 & 1 of CN1
on the operation U22 PCB assy. vary
0.7 – 4.3 V DC?
When the upper shaft pulley is slowly
turned by hand, does the voltage
between pins 2 & 1, pins 4 &1 and
pins 5 & 1 on the main NF3D PCB
assy. vary 0 – 5 V DC?
5 - 8
or
or
Y
Y
Replace main NF3D PCB assy.
N
Replace SS-VR F2 PCB assy.
N
Replace NP F2 PCB assy.