DURKOPP ADLER 767 Service Manual

15.4 Thread clamp (thread pulling device)
With the thread clamp 2 and the corresponding electronics the needle
thread is drawn downwards and a loop is formed at the sewing start. In
order that the thread does not break (it may be clamped between foot
and fabric) the sewing foot is released for a short time.
The degree of release is coupled with the position of the setting wheel 1
(stroke adjustment).
High stroke = high degree of release (thick material)
Low stroke = low degree of release (thin material)
The correct function of the thread clamp 2 depends on the s etting of the
potentiometer (normally this is set correctly).
Main setting rules
1. The thread pulling knife slightly rests on top of the centerpiece
support.
Correction: setting 1.
2. The cutting pressure should be as low as possible.
Correction: Setting 2.
3. The overlap should amount to 0.5 mm.
Correction: Setting 5.
4. The thread pulling knife must have no clearance to the rear when in
cutting position.
Correction: Setting 6.
15.5 Possible faults, cause and remedy for the short thread trimmer
Fault Cause and remedy
Thread is not cut - Check parameter;
- Blunt or faulty knife;
- Cutting pressure drawknife - counter-knife;
- Position drawknife;
- Cutting cam
Needle thread too
short
- Pretension too strong;
- Cutting cam too early
Thread clamp does not
clamp
- Foreign matter in the thread guidance;
- Check parameter;
- Check connection at the printed circuit board
Needle thread is not
drawn downwards or
thread breaks at the
seam beginning
- Check parameter;
- Check stroke adjustment;
- Foot lift too slow;
- Check throttle;
- Thread clamp does not clamp;
- Check connection at the printed circuit board
Thread pulling knife
does not catch the
thread
- Check the position of the cutting cam;
- Thread pulling knife does not run smoothly;
- Thread pulling knife not in initial position;
Thread pulling knife is
not brought to the
catching position
- Magnet not adjusted correctly;
- Pressure of the counter-knife too strong
Notes!
Attention!
It has to be checked whether the hook casing is pressed against the
guide of the base plate by the eccentric of the upper fastening screw.
(Service instructions item 4.3; description of correction).
Attention! The needle thread is not caught and forms a loop
around the thread pulling knife
Check the adjustment of the cutting curve and adjust according to the
top dead centre of the thread lever.
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DURKOPP ADLER 767 Specifications

General

Brand	DURKOPP ADLER
Model	767
Category	Sewing Machine
Language	English