Newly Serviced, Same Old Problem

Patrick

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Jan 8, 2022
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Hello All. I recently serviced a Waltham 17j. The movement, and balance staff, are in excellent condition... I didn’t replace the original mainspring because it too looked in excellent condition. However, the beat error is terrible. Would putting in a new mainspring resolve the issue? Thanks for your help.
 

svenedin

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No the beat error is nothing to do with the mainspring. It is caused by the impulse jewel being rotated/misaligned relative its correct “at rest position”.. When the balance is in the watch on its own (no pallet fork), the impulse jewel should sit in between the banking pins. It is analogous to a pendulum clock being out of beat. In modern watches the beat error is easy to correct but in old watches it is not and adjustments have the potential to wreck the hairspring. On an old watch the hairspring collet has to be rotated to the correct position on the balance stuff. On a modern watch a two-piece regulator allows the hairspring securing stud in the balance cock to be rotated like the regulator. Read up about this and for what it’s worth, I’d leave the watch with a significant beat error unless you are skilled and confident to correct it.

See this video for an explanation:

 
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Bila

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Jan 22, 2010
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Hello All. I recently serviced a Waltham 17j. The movement, and balance staff, are in excellent condition... I didn’t replace the original mainspring because it too looked in excellent condition. However, the beat error is terrible. Would putting in a new mainspring resolve the issue? Thanks for your help.
Beat error has to do with the relation between the Safety Table/Roller Jewel and the Hairspring stud, not the mainspring.
 
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svenedin

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By the way, do you actually mean beat error or poor amplitude of the balance?
 
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Patrick

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Jan 8, 2022
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No the beat error is nothing to do with the mainspring. It is caused by the impulse jewel being rotated/misaligned relative its correct “at rest position”.. When the balance is in the watch on its own (no pallet fork), the impulse jewel should sit in between the banking pins. It is analogous to a pendulum clock being out of beat. In modern watches the beat error is easy to correct but in old watches it is not and adjustments have the potential to wreck the hairspring. On an old watch the hairspring collet has to be rotated to the correct position on the balance stuff. On a modern watch a two-piece regulator allows the hairspring securing stud in the balance cock to be rotated like the regulator. Read up about this and for what it’s worth, I’d leave the watch with a significant beat error unless you are skilled and confident to correct it.

See this video for an explanation:

Thank You
 

svenedin

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Beat error. It’s 4.0
Is the watch running well otherwise? I would be inclined to leave it as it is. The risk of damaging the hairspring is high without the proper tools and practice. This is especially true because it will probably require multiple small adjustments and every time taking the balance out and back again.
 
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Patrick

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Jan 8, 2022
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Is the watch running well otherwise? I would be inclined to leave it as it is. The risk of damaging the hairspring is high without the proper tools and practice. This is especially true because it will probably require multiple small adjustments and every time taking the balance out and back again.
I was able to get the beat error down to 0.6ms. The watch seems to be running well. I just need a case for it.
 
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svenedin

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I was able to get the beat error down to 0.6ms. The watch seems to be running well. I just need a case for it.
Well done! As an amateur I’m too scared to adjust hairspring collets. There is a special tool for it but it’s not the only way to do it.
 
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