WS 22: Servicing a SEIKO 7005 including replacing the balance

Please note that this step is not necessary in a normal service! I did not trust my hairspring because of the strange curvature and decided to replace it. I am quite sure previous repairers had pulled the hairspring by disassembling and replacing the balance and thus the hairspring changed its curvature. The hairspring can easily sustain the wait of the balance wheel, but one still has to be very careful when lifting off the balance. This movement has a large diameter balance wheel that reaches under the top bridge and if one pulls up perpendicularly, one could easily tear the hairspring. The trick is to slowly lift the balance with a pair of tweezers and then slide the balance assembly out in a ca. 45 degree angle.
The picture below shows the turned brass block of the regulator turned 90 degrees and the loose spring of the spring stud cock. Now the balance can be easily separated from the balance cock

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