Valjoux 7750 Chrono issue

[MTWLFW]

Good morning all

I’m on my third 7750 pilots watch build all with brand new swiss supplied movements.  The third one seems to have an issue with the second and minutes chrono not running but the hour measure runs fine.  
I removed the seconds and minutes hands and reinstalled them but still they don’t run.   Has anyone come across this with a new movement?  
 

[clockboy]

Welcome to the forum, enjoy.. I have not repaired/ serviced a 7750 for a number of years but obviously some part has not been assembled correctly. I suggest you watch the many vids on YouTube to double check with the assembly.  This one is what I used by our Mark.

 

[AndyGSi]

Welcome to the forum.

Have you got the correct holder for the 7750 when fitting the hands?

[MTWLFW]

2 hours ago, clockboy said:

Welcome to the forum, enjoy.. I have not repaired/ serviced a 7750 for a number of years but obviously some part has not been assembled correctly. I suggest you watch the many vids on YouTube to double check with the assembly.  This one is what I used by our Mark.

 

Thank you clockboy.

[MTWLFW]

2 hours ago, AndyGSi said:

Welcome to the forum.

Have you got the correct holder for the 7750 when fitting the hands?

I do indeed Andy

[AndyGSi]

In that case I'd be looking at returning it as there's no reason a new movement shouldn't work.

[nickelsilver]

The seconds and minutes are run from the 4th wheel via a "rocking pinion" . This is pivoted in the plate, and at the upper end in a lever that does the rocking- which causes it to engage and disengage with the chronograph runner (the fine toothed wheel that carries the center seconds hand). The most likely problem is that the spring that functions with the lever has become dislocated. It is very fine, and not difficult to bump accidentally. The rocking pinion is part 39, the lever is part 40Var, and the spring is 47.

 

 

[MTWLFW]

2 hours ago, nickelsilver said:

The seconds and minutes are run from the 4th wheel via a "rocking pinion" . This is pivoted in the plate, and at the upper end in a lever that does the rocking- which causes it to engage and disengage with the chronograph runner (the fine toothed wheel that carries the center seconds hand). The most likely problem is that the spring that functions with the lever has become dislocated. It is very fine, and not difficult to bump accidentally. The rocking pinion is part 39, the lever is part 40Var, and the spring is 47.

 

 

Thank you Nickelsiver