Hi, I have a used machine, and the only information printed on it is "Meister 300". The bobbin mounts vertically under the foot, and I'm having a lot of trouble getting it working - it seems as though the mechanism is working, and certainly it runs fine dry, but no matter how I thread it, as soon as it has thread it jams almost instantly. I would love any help or advice you might be able to offer! Many thanks for your time, Alexander