What should I do if I don't have a good stitch?
-> Re-thread the threads, both the upper thread and lower thread
-> Insert new needle
-> Insert the needle high enough
-> Adjust the needle according to the type of fabric (stretch, microtex, ...)
 

I have loops?
- Loops at the top  -> Check the bottom thread tension
Is the bobbin nicely wound / placed correctly?

- Loops at the bottom -> Check the upper thread
Has the thread been threaded correctly, did you use yarn of quality?
 

How can I sew vinyl, leather, quilts and velvet?
-> Adjust the needle to the fabric
-> Use a modified foot such as:   
- Double-transport foot     
- Teflon or non-stick sole foot     
- Roller foot
 

The thread breaks
-> Use qualitative yarn
-> Test with different type of yarn
-> Replace needle
-> Check the tension and re-thread the machine
-> Make sure that the wire runs smoothly and cannot get stuck anywhere 
(For large bobbins, use a separate thread stand)
 

The sewing machine is not working?
-> Check if the cable is correctly connected to the socket
-> Check if the machine is switched on
-> Lower the presser foot when sewing
-> Check if the bobbin winder isn't switched on