With the base movement set up, the chronograph parts are added, starting with the cam and springs:

Valjoux ETA 7750 service and build - chrono build 1

Then the start/stop lever and bridge.

Valjoux ETA 7750 service and build - chrono build 2

All parts checked for wear and cleanliness as the build progresses.  This is a chronograph runner.

Valjoux ETA 7750 service and build - chrono runner

Showing the chronograph runners in place.

Valjoux ETA 7750 service and build - chrono build 3

And the hammers and bridge fitted.

Valjoux ETA 7750 service and build - chrono build 4

Finally the remaining springs.

Valjoux ETA 7750 service and build - chrono build 5

With the second and minute counting chronograph parts complete, the movement is turned over and fitted to a 7750 movement holder.  This supports the movement correctly for hand fitting and also has pushers to mimic the final cased watch in order to test the chronograph functions.

Valjoux ETA 7750 service and build - calendar build 1

At the lower, the hour counter runner, hammer and brake is fitted.  At the upper, the calendar mechanism with one part requiring rotation as shown in green so that the date and day change at the same time.

Valjoux ETA 7750 service and build - calendar build 2

Then the front plate and calendar mechanism.  The movement is ready for the dial and hands and all functions are checked at this point.  there’s a little more detail in these posts for an 1861 Omega.

Valjoux ETA 7750 service and build - calendar build 3

Finally, the dial and hands are added and the movement is ready to be re-cased.

Valjoux ETA 7750 service and build - dial and hands added

When cased, the final performance is checked and I use the specification from the ETA official website for this:

Valjoux ETA 7750 service and build - specification

As usual with these, the performance across six positions is excellent and this shows the fastest and slowest, 30 minutes after full wind and the variation is 6.3 seconds.

Valjoux ETA 7750 service and build - performance fastest

Valjoux ETA 7750 service and build - performance slowest

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