Problems With Vertical Needle Movement And Reverse Stitching - Brother NV4000D Service Manual

Failure Investigation for Electronic Parts
Problems with vertical needle movement
and reverse stitching
5 - 14
Is the resistance for the start / stop
switch, reverse switch, raise needle
switch, thread cut switch, presser foot
lifter switch, and thread switch normal?
Switch resistance values
Switch depressed : 1 Ω or less
Switch : out ∞
Y
When the upper shaft pulley is
slowly turned by hand, does the
voltage between pins 2 & 1, 4 & 1,
5 & 1, and 6 & 1 on the main PCB
assembly (CN15) change between
0 and 3 V DC?
Y
Replace main PCB assy.
Problems with vertical needle movement and
reverse stitching
N
N
Replace the SS PCB assembly
or thread switch PCB assembly.
Replace NP D6 PCB assy.