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Mainspring Valjoux 7750

rogart63
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rogart63 Distinguished Member

rogart63

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Need to change the mainspring on a 7750 . Do i need to take the complete movement apart. Was some times since working on a valjoux  and i have forgot how it's is . The movement should be serviced recently said the owner. But it won't wind with the rotor  . I looked and i can feel that the mainspring jumps when winding manually. Have had the reverse wheel out but that didn't help. Don't want to take the complete movement apart with the hands and such if i don't have to. Would be great if i just can remove the parts inside the case. But is that possible on a 7750. Or is the chronograph parts in the way and need to be removed. 

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HSL Distinguished Member

HSL

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A recently serviced 7750 with a broken mainspring should raise an eyebrow or two, I would have made a complete overhaul while being at it.
You can access it from the back but the amount of junk you have to take away makes it not worth for example leaving stuff on the train Wheel bridge to cut some work. I guess you already got the service manual but I attache it here anyway just for the public interest ;) 
 

7750 Service Manual.pdf

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