The k**b makes a squeaking sound and then stops

Question

The machine was doing fine for a while but then the k**b (or do you call it a head?) started to make a squeaking noise. It felt very heavy and then stopped. I could not even turn the k**b with my hand. I think it needs lubrication. Where do I lubricate? Do I have to take it apart? Can I use WD40 or do I need a special oil?I would appreciate your help very much.Thank you.