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Valjoux 7750 mainspring health



I'd like to hear some advice wether this MS is in good shape or if it should be replaced.

This comes from a 15 years old Omega Speedmaster Reduced, fitting a 7750, which has never been serviced before and stopped working.

I stripped the movement down to the mainspring since I thought in the first place I would have replaced it anyway.

But now I'm thinking that if it is in good shape it could be placed back in the barrel.

Should it be refitted the problem is I have no tool for MS, but that's a problem I'll deal with subsequently.

As you can see it is not flat to the surface and I remeber reading this is not good.

Any thought will be appreciated!

TIA Giuseppe




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It needs replacing. As you say its not flat, so it has become out of shape. When a spring is out of shape and it is wound up, it will rise and rub the barrel on the inside; this can cause poor flow of power to the train and erratic time keeping.  A new spring will come wound up and all you do is press the new spring in to the barrel. Just make sure before pressing in you have the spring the right way.  

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I would place a hefty wager that if you put that spring back in and ran tests on amplitude and running reserve, then replaced it with new, same tests, you'd see zero difference. True it's very slightly out of flat but not enough to have an effect. It otherwise looks perfect.

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