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Tim Mosso and Mike Michaels discuss the Valjoux 7750 automatic chronograph caliber. Mike discusses the strengths and weaknesses of the 7750 - also known as the ETA 7750. The ratchet driving wheel is a typical weak point of the 7750, and Mike explains that the ratchet driving wheel is a critical component of the automatic system. Knowledgeable watchmakers check this component before approving the sale of a 7750 to a client. Tim follows this discussion with an explanation of the different methods of driving an automatic movement; certain systems like the Rolex jeweled staff with bi-directional winding are exceptionally quiet but vulnerable; ceramic bearings with unidirectional winding are tough and efficient but generate noise and "rotor wobble."
Video and content by Tim Mosso and Pheline Jerome.
