you can open a door on the end of the head, where the light bulb is. I had a look in there but couldn't see anything. I've put it away in disgust and got the old one back out! I thought of getting DH to have a look at it tomorrow - he's home late tonight and probably the last thing he'll want to do is surgery on my sewing machine! I just thought maybe someone here had had the same problem and could think of something I missed! How would I check the threading path other than what I've done?