Singer 9920 Service Manual page 30

Condition of switches and sensors
The condition of each switch and sensor is indicated as
follows.
b: Buttonhole lever switch -Rear
1=Neutral 0=Lever is pulled.
f: Buttonhole lever switch -Front
1=Neutral 0=Lever is pushed.
Lower the buttonhole lever and check these switch by
pulling or pushing this lever.
S: Stop sensor 1=not intercepted
T: Timing sensor 1=not intercepted
s: Speed sensor 1=not intercepted
These sensors are intercepted by the slit plates on the
upper shaft.
Stop sensor = Stop slit,
Timing sensor = Timing slit,
Speed sensor = Speed slit
Turn the handwheel and check the response of each
sensor.
W: Bobbin Winder Switch
1=Bobbin winder spindle is in right position
0=Spindle is in left position
Move the bobbin winder spindle left or right and check
this switch.
w: Bobbin Winding Stop Switch
1=Bobbin winder stop is not pushed
(Bobbin winding is not full)
0=Bobbin winder stop is pushed to the right
(Bobbin winding is full.)
Move the bobbin winder stopper to the right and check
this switch.
O:Presser foot switch
1=Presser foot is lowered
0=Presser foot is lifted
Lower or lift the presser foot lifter and check the
response of this swtich.
Y: Upper thread sensor (Only 9940)
1=Thread check spring is pulled
0=Thread check spring is not pulled
Thread the upper thread until thread check spring
(threading route No. 4) and hold both end of thread.
Pull or release left end of thread and check the
response of this sensor.
b f
0=intercepted
S T
0=intercepted
0=intercepted
W w
O Y
f
b
s
W
w
O
SERVICE MANUAL
s T
S
Y
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