7751 Chronograph Components Assembly

Today I finished the overhaul of the 7751.  It just takes a bit longer than the 7750 because of the extra parts on the dial side.  Overall the process took around 5 hours to complete.  These practice sessions are important because we have to service 7750 chronographs for both the SAWTA 4 and CW21 testing.  Next week I will be working on a 7750 installed in a Tudor case that has been thoroughly mucked up by my instructor.  I will try and post results.

Chronograph base components technical documentation

Here is the cam jumper and cam installed.  The cam synchronizes and controls the functions of the chrongraph.

Here the lock and the ratchet wheel driving wheel have been installed

Chronograph bridge, installed

Here is the operating lever spring, lubricated and installed.  This is what pushes back on the chronograph buttons when they are depressed

Here is the operating lever, notice some more of the white grease on the end where it interacts with the cam

Testing the operating lever and its interaction with the cam

The next phase

Here the chronograph and minute counting wheels have been installed along with the tiny oscillating pinion which is the disconnect between the watch and the chronograph mechanisms

Here is the clutch, reversing wheel and reduction wheel installed

The automatic bridge, installed.  The hammer has also been added before the bridge is installed

The long curved thick spring on the left side is the hammer spring, it puts pressure on the return to zero hammer

Here is the depthing engagement between the oscillating pinion and the chronograph wheel.  The depth is controlled by the clutch and its eccentric, here depthing is slightly shallow as you want about 2/3 engagement

Increased engagement slightly, enough to have good positive contact but not enough to increase friction beyond tolerance

Finally the minute counter jumper spring must rest perfectly on 2 teeth of the minute counter when the hammer has been activated.  This prevents the minute counter hand from moving when the hammer is reset

Time to flip the watch over and work on the dial side components

The driving pinion is pressed on.  This is the friction point in the watch that allows the hands to move freely during setting but in normal operation is still moved by the mechanism

Here is some more of the motion work, the minute wheel and free cannon pinion have been installed

Here are the hour counter return to zero components and wheel

Here is the day corrector and its spring

Here are the 12 and 24 hour wheels installed

Finally, on this level, the calendar driving wheel

The penultimate page!  This is all jumpers and correctors

Date star wheel installed with the date corrector

Here are all of the jumpers and springs.  These index the day and month dials, along with the moonphase indicator

The final page of assembly, some final plates and the indicators

Here are the 3 indicator wheels installed along with the moonphase platform and combined maintaining plate

Dial is installed, hands are installed

Using a hand press to apply subdial hands

Completed movement, ready for casing

Cased and finished