The ETA 7750 (originally Valjoux) is pretty much the industry standard chronograph and has the full chronograph features plus day and date complications as well as being an automatic calibre. These are usually a pleasure to work on and this Zeno is no exception.
A lot of parts in these – this container just showing the basic movement parts and I’ve already closed the barrel with a new mainspring.
And this second container has all the chronograph, day/date and automatic complication parts.
With everything clean, the balance jewels are fitted and the balance is mounted on the plate.
These use the Etachron system for the hairspring mount and adjustments – this is a very nice system and adjustments can be made precisely.
The fitting in red controls the regulator pin gap and firstly that is turned to open the gap.
The one in green is where the hairspring stud is mounted and that is then turned until the hairspring is dead central in the regulator pins. If it leads to a slightly non concentric hairspring, then the hairspring shape can be adjusted by hand locally between the green and red (it should not be touched anywhere else).
Then the red fitting is turned to close the pin gap at the regulator to approximately 2 or 3 times the hairspring thickness and, it’s done.
Final check that the hairspring is horizontal and parallel to the plate plus that it stays central to the regulator pins over a range of adjustment.
Although I’m only showing about a quarter of the photos in typical report, each of the parts is checked for cleanliness and wear – some examples as below. Jewels, bearings and posts in the plate and bridges are reviewed under a microscope.
And parts such as the keyless works.
Plus the wheels (gears) that run the watch.
And the pivots of the wheels.
After removing the balance temporarily fitted earlier, the keyless works are mounted on the dial side.
Turned over and the train is fitted in place.
Then the main bridge plus the crown and ratchet wheels.
And the fork and balance so that the basic movement is complete and now runs. There are some adjustments made here so that all is fine before fitting the complications.