Stop motion knob not working
Hi,
I've just got a Jones 641 sewing machine but I can't seem to work out how to wind the bobbin. I've looked in the manual online and I'm meant to turn the stop motion knob to loosen it... Well I loosen it, the knob itself is loose but the machine sews anyway! The bobbin pin doesn't spin and the machine continues as if it wasn't loose. The knob spins approx 90 degrees loosely before i can feel it 'hit' something hard on one side or tighten the other way. Whichever way I go, after that 90 degrees the whole thing spins with it. Someone help please!