Bobbin problems with brother pe 770

Is the brown different compared to the other colours you were using? (rayon instead of polyester/another make of thread/a different thickness etc.?) For some reason you need to lower the top tension when using it, to stop it pulling the bobbin cotton to the top.

As Alison has said, variations in thread can be a significant cause, but this can even extend to the colour. Although it is not as much of an issue as when rayon first appeared for embroidery (it all used to be done in mercerised cotton!) sometimes darker colours can give rise to tension issues.

The first thing, however, is to determine if it is just a top thread issue.

Basically, for all threads the tension needs to be as loose as possible yet still have a perfectly even stitching on top. Then the balance between top and bottom should be so that, for a 5mm column of satin stitch the back should show one third of bottom thread down the centre of two thirds of top thread.

However, tension varies with stitch length and machine speed and it may be this that is causing issues. If the brown stitches are smaller and running faster then a slightly loose bobbin will give rise to what you are seeing, even if the other colours are fine.

Whatever you do, though, always bear in mind my first point: Don't just keep tightening the bobbin to cure the problem. In my experience it is one of the most common machinist faults that they keep tightening tensions without a real understanding and then wonder why the quality of sewing diminishes, or the number of thread breaks goes up!