miércoles, 2 de septiembre de 2009


If there is a single movement ubiquitous in modestly-priced contemporary chronographs, it is the Valjoux 7750. Introduced in 1974--five years after the famed Zenith El Primero automatic--the movement has been supplied in both 21,600 and 28,800 beat versions. It uses an automatic-winding module attached to the top of the movement, winding in one direction by means of a single double-click wheel. Initially using 17 jewels, current versions run in 25. The 7750 is 13.25 ligne (30 millimeter) design, 7.9 millimeters thick.


Like many contemporary chronographs, the Valjoux 7750 dispenses with the traditional column wheel for switching functions. Instead a heart piece limiter (left) is used to coordinate starting, stopping, braking, and reset functions, usually by means of two buttons in contemporary designs (the earliest coulisse-lever calibers used three buttons). The Valjoux 7750 also utilizes a concept first patented in 1941 by a watchmaker, Henri Jacot-Guyot. This is a reset-to-zero (or heart piece) lever which pivots to reassure accurate reset-to-zero of both the center hand and minute counter. Previous coulisse lever designs had not been as precise in this regard.

While the parts count of a coulisse-lever design is comparable to that of a column wheel design, the various levers and springs in the lever design require much less precision in form and materials and are much less expensive to manufacture. This--economy of manufacture--was and is the purpose of a coulisse lever caliber


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The Valjoux 7750 expresses an aspect of Swiss engineering skill that we do not normally associate with the Swiss watch industry: economy of manufacture. The 7750 is a good representation of the new, simplified chronographs that began to appear from Ebauches S.A. (now ETA) at the beginning of the 1940s and that provided serious, usually fatal, competition to smaller manufacturers of high-grade chronographs.

The Valjoux 7750 is now used in the vast majority of mechanical chronographs produced in Switzerland, and has allowed the mechanical chronograph function in watches of modest cost. For a caliber obviously engineered from the ground up for economy of manufacture, the 7750 has proved itself a reliable and durable workhorse. Without the 7750, mechanical chronographs might be known only to the buyers of luxury watches.

I wish to thank Bob Frei of the TZ Tool Shop and Frei & Borel for supplying the movement used in this review.

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