Hello Penny,
With the F/R 64, make sure first of all the belts are tight, if the motor is working and turning the balance wheel, it may be that the washer has slipped inside the balance wheel, if you turn the balance wheel by hand but the needle does not go up and down that could be the cause, turn the balance wheel by turning the stop motion wheel in the middle of the balance wheel, if you can't turn it then you may have thread stuck in the raceway, if all fails post another question, as far as your 502 is concerned the chances are that what you are feeling is static, the motor is suspended on two nylon pins and the foot control is double insulated so pretty unlikely it is an electrical fault
ken
February 2011