I have a Janome 1600P which I use on a Happy Jack frame for quilting. Ever since I acquired the machine I have had issues with the thread breaking, and missing stitches particularly when moving in a diagonal backwards direction. Up to now I have thought that this was a problem with my technique only. Such things as regularly changing needles, oiling, cleaning, and particular care not to go too fast in that direction have improved the situation. Sewing more left to right rather than right to left on the frame.
Well the reason for this post is ...... I just got some some new bobbins. I am not sure that they are actually Janome bobbins - but they were sold to fit this machine. The difference is extraordinary. A whole quilt with no broken threads.... no skipped stitches .... The machine is quieter. I would not have ever considered that the bobbins were the issue as I had 11 genuine bobbins which I got with the machine and the problem existed with all of them,............
Apart from this I am very happy with the machine - I have quilted over 120 quilts with it in the past 3 years.
Answers to questions (addition to original post)
I purchased the bobbins from Sharp sewing supplies PO Box 41721 Los Angeles CA 90041 USA.
Toll free phone: 800-2252983
Ebay shop: http://shop.ebay.com.au/sharpsewing/m.html
They are the aluminum bobbins... I am in no way connected with this store other than a happy customer.
A friend of mine who has more sewing machine mechanic knowledge than me has pointed out 3 things: these bobbins are lighter than the original bobbins and minutely smaller both in width and thickness.