JUKI LU-2800 Series Engineer's Manual page 132

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble
From the previous page
3-6) Both needle and bobbin thread cannot
be trimmed.
4. Thread slips off 4-1) Thread tension given by the tension
the needle eyelet controller No. 1 is too high.
simultaneously with
thread trimming.
4-2) Thread take-up spring stroke is too
large.
4-3) Thread trimming is carried out at a posi-
tion where no material is present.
Cause
6-A) The blades of moving knife and counter
knife have been improperly adjusted.
6-B) Counter knife pressure is excessively
low.
6-C) Moving knife fails to work.
6-D) Presser foot drops from cloth at the time
of thread trimming.
Checking
Refer to "2.-(16)-6) Adjusting the knife pressure".
Refer to "2.-(16)-6) Adjusting the knife pressure".
Refer to "2.-(16)-5) Position of the thread trimmer
cam", and "2.-(16)-4) Thread trimmer cam timing".
Replace the thread trimmer solenoid with a new one.
Perform thread trimming on cloth.
Decrease the thread tension given by the tension
controller No. 1.
Decrease the stroke.
To carry out outside-of-material-edge thread trim-
ming, change the thread guide to the needle thread
presser (40034675) supplied with the unit, and turn
OFF the needle thread clamp changeover switch.
(Only LU-2828-6 and 2828-7)
Corrective measures