JUKI MOL-254 Engineer's Manual page 234

No. Phenomenon
28 Nothing is displayed on the Screen is bright and back-light is lighting.
operation box panel.
Screen is dark and back-light is not lighting.
29 Data has disappeared from the The set data cannot be stored when turning OFF the power.
operation box panel.
30 O u t p u t o f t h e b e l t l o o p Output of the sensor does not change.
thickness detector sensor is
abnormal.
31 The sewing machine does not Alarm No. is not displayed on the operation box panel.
start even when pressing the
start switch.
32 Thread trimming operation is The 1st hook thread trimmer fails to operate.
abnormal.
The 2nd hook thread trimmer fails to operate.
33 The power is cut when using Thermal protect of the power switch for high voltage is operating.
the machine under the high
voltage specifications.
Detailed state
There is a possibility of blown-out of fuse F6 (6.3AT) mounted on the PWR
circuit board. Check it.
It is considered that connector CN19 or CN40 is disconnected, or the cable has
broken. Correctly connect it.
There is a possibility of blown-out of fuse F5 (6.3AT) mounted on the PWR
circuit board. Check it.
It is considered that connector CN9 is disconnected, or the cable has broken.
Correctly connect it.
It is considered that battery back-up is abnormal. Replace the MAIN circuit
board.
At this time, be sure to re-turn ON the power and make a memorandum of the
origin set values such as <BB>, <BG>, <BH>, <BI>, etc. in order to re-input
important data in the replacing circuit board.
It is considered that connector CN13 is disconnected, or the cable has broken.
Correctly connect it.
Effective range of output of this sensor is the specified range of 90˚ only. It is
considered that there is a possibility of maladjustment of outside of the range.
Check the sensor for the state of adjustment.
Check whether the sewing machine is in the sewing possible state that the set
ready LED lights up.
It is considered that connector CN15 is disconnected, or the cable has broken.
Correctly connect it.
It is considered that the start switch and the switch lever are improperly adjusted.
Perform re-adjustment.
The cause is due to the drive of air cylinder when the operation indication lamp
of the solenoid valve lights up. Check the air piping.
It is considered that connector No. 11 directly attached to the solenoid valve,
connector CN8 or CN113 is disconnected, or the cable has broken. Correctly
connect it.
It is considered that connector CN3 or CN111 is disconnected, or the cable has
broken because of the operation by the thread trimmer solenoid. Correctly
connect it.
Check whether the thermal set value as against the operating power voltage is
correct.
For the power voltage, 220v, 230V and 240V, set the value to [4.0] and for the
power voltage, 380V and 400V, set the value to [2.5].
Checking point and corrective measure Replacing part
Fuse
Operation box panel
Fuse
Operation box panel
MAIN circuit board
Loop thickness detector SW
Start SW
MAIN circuit board
Solenoid valve
MAIN circuit board
Power SW