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interesting problem with a valjoux 7730....timing well...all is good except for one item...when the upper pusher is depressed to stop the chronograph runner the hand falls...this only happens between 07:00 and 011:00....I notice that the runner is not stopped by a brake and the heart drops toward 06:00 when vertical and the upper pusher is depressed to stop the chronograph hand...the hand is tight on the runner...why does the hand fall?...thanks

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I don't really understand. As far as I know the Friction spring should put pressure to the disc with the tooth on the downside of the chronograph runner wheel and the long pivot should run through the "fork" of the spring. Could you take a Photo of the situation?

 

 

 

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1 hour ago, rattandsonwatchmakers said:

I did check the friction spring, it has a slight upward bend, putting pressure on the  underside of heart cam, forcing it into the jewel...would you suggest removing the spring and increasing the bend?....thanks! 

Early 7730 movements had no brake, as you've noticed. You can increase the tension on the friction spring quite a bit, and definitely need to. Make the bend near the screw, it should be several millimeters above the plate at the end that contacts the chronograph runner. Check that amplitude doesn't drop more than 30 degrees or so with chrono engaged.

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