Sticky clutch older pfaff 7570

Question

When filling a bobbin the clutch does not disengage. The needle goes up and down. When it does disengage the bobbin runs at high speed and will only stop when I push a button on the machine. I explained this problem to the technician at the sewing machine shop. He said the clutch is dry. How do I access it? What does it look like? What do I need to do to oil it?Thanks