Under the Loupe/ETA 7750

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ETA 7750

Originally released by Valjoux in 1974, as the Valjoux 7750, the ETA 7750 is quite simply the most widely adopted mechanical chronograph movement in use today, and can be credited with bringing mechanical chronographs to the masses.



The video above shows the calibre being assembled by a watchmaker. Please note that lubricating steps have been edited out to keep the video short. A complete technical revision of a watch with this calibre should take between three and four hours if it is to be performed properly. Alliance Horlogère does not recommend that owners without the proper training or experience attempt to undertake service of their timepieces. Please consult a qualified horologist.


Dismantling the calibre starts with removal of the automatic winding mechanism, followed by removal of any calendar and other complications on the front. The chronograph mechanism itself is then dismantled, followed by the basic time only components of the watch.


The rhodium plating on the automatic bridge is easily scratched when removing and replacing the hammer spring. With a little practice, a simple brass rod (like the one used in the video above) filed to a small taper, makes quick work of this task while also protecting the automatic bridge. The rhodium plating cannot be marked by the brass even when excessive pressure is applied.

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