Expert: Dave Nyce - 1/6/2003

Question
Hi Dave,  I am replacing the cpu cooling fan on my computer and the power wires come from the fan, then are coiled around a ring about 3/4 inch in diameter, then go to the pins on a board.  What is the ring for and is it necessary since the new fan doesn't have it.  Thanks.  

Answer
It is a ferrite ring and the wire coiling around it makes an inductor. It is for the purpose of reducing the electrical noise being induced into the computer circuit from the fan motor. Each type of motor has its own characteristics. Your new fan may or may not need the ferrite ring, there's no way to tell without very expensive equipment.

If the fan was made as a replacement for your particular model of computer, it is probably ok to use just as it was supplied to you. If it is possible to put the ferrite into the new fan circuit, that would not hurt.

If the fan is noisy and there is no ferrite used, the problem would be that errors are made by the computer due to the electrical noise.

Hope this helps!

Dave