WS 19: Servicing a SEIKO Chronograph 6138
As mentioned before, this balance is almost 12 mm in diameter and 3 mm larger then e.g. the balance wheel in a Caliber 7005 which also matches the Caliber 7S26 in our Monsters. Rob said - I would not have noticed this - that the hairspring had a slight distortion and he fixed that after the balance had been in the ultrasonic bath. Also interesting, the hairspring got an extra rinsing with Thinner (we used a Japanese product Mr. Thinner from the Mr. Color brand). One wants to make sure that after the ultrasonic cleaning that there is absolutely no residue on the hairspring since this could disturb its oscillation and its beat (symmetrical ticks and tocks).
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