grandma jo of 6, I have the exact same machine...in the same cabinet. Bought it new in February 1972, and it still works great. It's never been serviced, other than the routine cleaning I do myself. What a workhorse of a machine!!

I had one of these machines,....turn the hand wheel to tighten and see if that fixes the problem....if I remember correctly, you had to turn to the left to loosen to wind the bobbin and then turn to the right to tighten and sew again.