E-40 how to set

SOURCE: industrial sewing machine top thread breaking

The brother DB 2 series of machines do not use a needle with a flat side. the needle system is DBX1 and are available from size 10 to size 20.
Try using the right needle for the machine and the right size for the thread you are using. this should make it better

SOURCE: Brother Industrial Machine Tension

This is an answer to another person with a similar complaint. Try the suggestion below, it may fix the problem.

From your description it appears that you have tried tension settings on the upper tension control adjustment knob without success.
Check that the bobin tension is adjusted correctly by taking out the bobin complete with the spool.
Pull the cotton thread and it should be a smooth light pressure if the tension is correct. If it is tight to pull or pulls freely then adjust the tension screw which is found on the outside of the bobbin. The screw is very small and requires a minature size screwdriver. The adjustment will only be a slight turn of the screw one way or the other to obtain the correct tension(depending if it was loose or tight).
Once this is set reinstall the bobin and tread up the machine, hopefully with the upper tension set at approx."2" the machine will sew correctly.

SOURCE: Brother DB2-B755-3 industrial sewing machine

I have the manual in pdf form here

http://myweb.tiscali.co.uk/stitches/BROTHER-DB2-B755-MKIII-MANUAL.pdf

SOURCE: Bobbin won't thread on my Broter DB2 B755-3

Manual here........


http://myweb.tiscali.co.uk/stitches/BROTHER-DB2-B755-MKIII-MANUAL.pdf

SOURCE: MANUAL FOR BROTHER INDUSTRIAL SEWING MACHINE DB2-B755-3

Go to brother.com . From there you will need to enter the model number and serial number to get the file for free good luck