Seiko 4502a servicing, a past repair gone awry

This very nice Seiko 4502a is in for servicing and is still struggling to walk again. It is in the ClockSavant recovery room where it awaits donor parts and another surgery. Few parts are available for it. The watch’s “click,” the part that holds the mainspring power while winding, broke. This released the mainspring’s power into the movement. The barrel bridge has wear around the click and crown wheel. The watch had a problematic hand winding and setting feel and “skipped” when winding during assembly testing which was in-part tracked down to a previously repaired yoke, visible only under a microscope as shown in the picture. This part is weak and under heavy force. A past watchmaker repaired it (part not available) and it was very slightly off causing, in-part, the winding and setting issue. During final assembly testing, the yoke failed—breaking where the repair was made. This yoke can be more difficult to make, should one go there, due to the raised nub used to push the large oscillating date change lever and overall tighter tolerances. The time and cost to fabricate one is not economically practical for this watch. It is now running very nicely again but is on the donor list awaiting a new yoke, winding pinion, and possibly a new clutch should they can be found over time.

Servicing a Seiko 4502a, service and repair of a Seiko 4502a