I just received a Wheeler & Wilson treadle sewing machine. Can anyone tell me how to put thread on the bobbin. The machine sews like a dream, but when the bobbin ran out of thread, I filled it and now when I start to sew, the top thread comes out of the needle. It is not due to the thread being too short. Is there a website where I can find a diagram of how the machine is threaded, etc.? Any help is appreciated.