WS 22: Servicing a SEIKO 7005 including replacing the balance

I was happy to see a movement in decent overall condition after removing the rotor. The rotor can easily be removed using the largest (normally 2 mm wide blade) screwdriver in a watchmaker's screw driver set.
Let us have a closer look at the magic lever on the next page, as this is probably one of the most ingenious invention for a simply yet stunningly efficient bi-directional automatic winding system.
If you want a more detailed explanation of the magic lever system, please look at John Davis' drawing at his great "Black Monster 7S26" review at Also Rob B talks about the Magic Lever in his article.

How does the Magic Lever work?

I tried to keep it very simple and combine all into one illustration. Please note that I used a dotted dark gray line to extend the double pawl lever in order to show the hidden eccentric mechanism. I have also exaggerated the teething of the winding wheel in orange. Added the axes of the of the two pawls with a fine orange line and indicated the sole rotation direction of the winding wheel in orange (below the A of JAPAN). Also note that this is a left threaded screw that will open if you turn it clock-wise. Watch manufacturers have different ways to mark those screws, SEIKO uses three slots to indicate this.

Rotor turns counter clockwise: the "magic wheel" (with the hole) turns clockwise and the lever pulls the winding wheel in the green arrow direction.

Rotor turns clockwise: the "magic wheel" turns counter clockwise and pulls the winding wheel in the red arrow direction.

And this is really all there is to this simple and efficient bi-directional winding system! Few parts, simple construction, durable - this is indeed a "magic" invention and no wonder SEIKO has been sticking to it for decades and also uses the magic lever in the today ubiquitous 7S26 and 7S36 calibers powering most of the contemporary SEIKO Diver's.

Please click on the last picture to read on >>>