Unicorn LS2-H550, Operation Manual

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TROUBLESHOOTING GUIDE
Problem Cause Check Solution Page
Needle thread
escapes at start
of sewing.
Tension disc does not
open sufficiently.
Tension disc
opening
Adjust tension release.
Excessive pretension ― Adjust pretension. 6
Needle too heavy for
thread
―
Use smaller size
needle.
Up needle stop position
too high, thread removed
by thread take-up. Thread take-up
height at up needle
stop position
Delay up needle stop
position timing.
15
Thre ad cu tter
mec hanism does
not fu nction .
Thread cutter solenoid
dose not function.
Check with tester
Replace thread cutter
solenoid.
Thread cutter signal not
transmitted.
―
Check circuits; refer
to motor adjustment
manual
Thre ad wiper
do es not
funct io n.
Needle thread remainder
too long.
― Adjust pretension 6
Timing too early; wipes
thread before tension
disc closes.
― Adjust timing.
Excessive material,
presser foot resistance
―
Replace with presser
foot having back
channel.
Thread wiper operation
too short
― Adjust operation time.
Mate rial en d is
not cut during
sewing.
Gap between upper and
lower knife
― Reposition upper knife 24
improper engagement of
upper and lower knives
―
Adjust overlap of two
knives
24
Upper knife is dull ― Replace upper knife
Mate rial is n ot
cut properly at
corn ers.
Upper knife positioned
too far forward
― Reposition upper knife 24
upper knife posotioned
too far to rear
― Reposition upper knife 24
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