HappyJapan HCH-701-30, Maintenance Manual

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Trouble shooting(Upper thread comes off from needle hole)
7-2-5
Trouble Factor Cause of trouble and measure
Page
Upper thread
Mechanical
1. Is keeper in motion?
comes off 1-1 Check if cable was cut or there is something unusual.
from needle 1-2 In case solenoid is in trouble, replace. 3-6-11
hole 1-3 In case CONT-J board ass'y is in trouble, replace.
2. Is keeper put in right place?
2-1 Put it as specified.
3-6-12
2-2 Modify bent of keeper.
2-3 Adjust it again if movement is not smooth.
3. Is magic-tape on thread catch holder not worn?
3-1 Replace magic-tape. 3-3-14
4. Does bobbin thread holder hold bobbin thread?
4-1 Adjust pressure when contacting moving knife.
3-6-10
4-2 In case bobbin thread holder is in trouble, replace.
4-3 Clean bobbin thread holder.
5. No error in thread cut (2 threads cut)?
5-2 Position moving knife as specified.
3-6-9
5-3 Check and polish burr or scratch on moving knife.
5-4 In case moving knife is in trouble, replace.
3-6-6
6. Are clearance between needle and rotary point and needle height are proper?
6-1 Adjust clearance between needle and rotary hook as specified.
3-5-1
6-2 Adjust needle depth. 3-3-6
7. Doesn't thread catch hook cut upper thread?
7-1 Polish burr on hook.
7-2 In case hook is in trouble, replace.
8. Does thread catch hook hold upper thread?
8-1 Check if cable was cut or there is something unusual.
8-2 In case pulse motor is in trouble, replace.
8-3 Adjust fixing position.
3-2-18
8-4 If hook is bent, modify.
8-5 In case hook is in trouble, replace.
8-6 In case CONT-J board ass'y is in trouble, replace.
9. Check tension of thread adjusting spring is too weak.
9-1 Adjust of tension.
3-3-11
( ) ---Reference instruction book s ---Standard c ---Color monitor