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Discussion Starter #1
I have a balance with a visually weak amplitude (no timing machine available, but it's obvious, especially when running next to an identical and healthy movement) that slows and even stops in certain positions, although rather unreliably (sometimes it'll stop as I rotate the movement around in the air, and sometimes it won't, so I haven't readily nailed down a single most-problematic position). I have confirmed that the problem is definitely the balance because I switched two balances between two identical movements (all are brand new) and the problem stayed with the balance, not the movement. I have tried oiling everything that could be of relevance, including obviously the front jewel and the rear jewel. I actually unlocked and removed the rear jewel cap (the one attached to the balance bridge) and oiled it (no point in bothering with the other jewel since I already established that the problem is somewhere on the balance bridge). At one point I thought the hairspring was a tad less concentric than other balances on identical movements, but I have since reshaped the hairspring some and feel that it is well within conventional variation on that particular matter. I haven't literally cleaned the balance in naptha or anything like that, but like I said, these movements are all absolutely brand new (well, I bought them one or two years ago, but they have sat in their plastic cases awaiting eventual watch builds).

I'm starting to think the balance isn't well poised, but I don't have the tools to confirm, measure, or repair that, nor are the movements worth enough to fix such issues, but since I already purchased an escape wheel (broke a pinion, duh!), I'd love to get this balance fixed or else the new escape wheel will have been a wasted purchase.

What problem could cause a weak amplitude and slowing or stopping in a somewhat-position-dependent manner, on an otherwise clean and new movement, but such that basic oiling of the balance and some hairspring maintenance doesn't fix it?

I could post a photo later tonight, but I don't think there's much to see. Things are basically healthy-looking at this point. Perhaps a video would help. :)

I'm at a loss.

Thanks.
 

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The obvious would be a bent or otherwise damaged pivot. That's far more likely to cause such problems than poise, which would have to be a LONG way out to give a visible effect like that. It's also more likely for a pivot to get damaged in an unused movement than for the balance to magically un-poise itself!
 

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Is the hairspring flat? I had a problem with a Gruen once where the overcoil was lifted ever so slightly, so that when the balance was installed and the cock screw tightened down, the hairspring 'coned' downward just a little. This caused it to very slightly touch the balance arms and the friction robbed the balance of momentum. So, despite having great backlash of the train and the pallet snapping beautifully from bank to bank, it had about 140 degrees of amplitude at full wind.
 

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. . . I switched two balances between two identical movements (all are brand new) . . . .
Who is the manufacturer?

What is the caliber designation?

. . . these movements are all absolutely brand new (well, I bought them one or two years ago, but they have sat in their plastic cases awaiting eventual watch builds). . . .
Where did you purchase them?

. . . since I already purchased an escape wheel (broke a pinion, duh!), . . . .
The movements are new and have been stored in plastic cases and yet require an escape wheel?

. . . but I don't think there's much to see. Things are basically healthy-looking at this point. . . . .
I don't think that any present would object to the posting of high resolution shots of the:

upper pivot

lower pivot

hairspring from the top

haispring from the bottom

hairspring from the roller jewel

hairspring from the stud
 

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Discussion Starter #7
Who is the manufacturer?
It's one of the common Chinese 6497 skeletons. I believe the consensus is that it is a Hangzhou 9211 as opposed to a Sea-Gull, owing to its use of a single-screw palette bridge and larger 18,000 bph balance wheel.

What is the caliber designation?
6497-clone, I believe it's the Hangzhou 9211 (with various suffixes to distinguish silver/gold/gunmetal/etc.).

Where did you purchase them?
Some Chinese supplier I forged a good relationship with at the time. Of the 21 movements I obtained (some of this caliber and some the common Sea-Gull ST3621 6498 clone) I've had very little trouble. There are bound to be a found lemons in larger batch orders, but I would still like to try to fix it if possible.

The movements are new and have been stored in plastic cases and yet require an escape wheel?
As I was testing all the movements, I isolated those that exhibited any trouble for further investigation. This movement's weak balance was one of the worst offenders. In my deconstruction, investigation, cleaning, and other various actions, I broke the escape wheel pivot while reconstructing the movement (almost certainly due to lack of delicateness when fitting the train bridge over the third, fourth, and escape wheels). No big deal, learning pains of this sort are to be expected.

I don't think that any present would object to the posting of high resolution shots of the:
Okay, thanks. Perhaps later when I get a chance. Much appreciated.
 

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Discussion Starter #8
The obvious would be a bent or otherwise damaged pivot. That's far more likely to cause such problems than poise, which would have to be a LONG way out to give a visible effect like that. It's also more likely for a pivot to get damaged in an unused movement than for the balance to magically un-poise itself!
Thanks. I don't believe I've observed any pivot damage in my copious magnified investigation, but I'll consider that as a suspect to more closely scrutinize.
 

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Discussion Starter #9
Is the hairspring flat? I had a problem with a Gruen once where the overcoil was lifted ever so slightly, so that when the balance was installed and the cock screw tightened down, the hairspring 'coned' downward just a little. This caused it to very slightly touch the balance arms and the friction robbed the balance of momentum. So, despite having great backlash of the train and the pallet snapping beautifully from bank to bank, it had about 140 degrees of amplitude at full wind.
Yeah, I believe so. I was a little unconfident about its concentricity, but reshaped it a tad and feel that it is concentric enough (it resembles other identical movements at this point).
 

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Thanks. I don't believe I've observed any pivot damage in my copious magnified investigation, but I'll consider that as a suspect to more closely scrutinize.
Bear in mind that the symptoms you're describing can be caused by a very slight bend.

Also, just a thought, did you swap just the balance when fault finding or the balance and cock complete? If you swapped both then it could also be a problem with the cock - cracked, dirty or loose jewel hole?
 

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Discussion Starter #11
Bear in mind that the symptoms you're describing can be caused by a very slight bend.

Also, just a thought, did you swap just the balance when fault finding or the balance and cock complete? If you swapped both then it could also be a problem with the cock - cracked, dirty or loose jewel hole?
I'm referring the entire structure physically connected to the balance bridge. So the entire system from the impulse jewel foward through the balance bridge. When I say I "isolated" the problem to that structure, I mean that I determined cause of the problem is not in the palette, escape wheel, fourth, third, or center wheels, main spring, winding mechanism etc. I unscrewed the entire balance bridge from two movements and interchanged them between the two movements, so bridge/balance-wheel/spring/pivot/various-spring-attachments-and-end-parts/back-side-pivot-and-end-cap-jewels(incabloc).

I'm still new to disassembling watches. I've never deconstructed the balance assembly in fact, just the major bridges and wheels that pop out if you remove the bridges.

Thanks.
 

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That's what I suspected when I re-read the first post for clues, and there's nothing wrong with that - far better to be aware of your limitations than dive in head first like we've seen some do on here then be posting about "does anyone know how to rebuild this mangled part?" :D

In this case, though, it may be time to take a deep breath and the next step by removing the balance from the cock / bridge (technically cock if it's only supported at one end btw). You'll really need to do that anyway to the faulty one to be able to inspect the top pivot properly without risking hairspring distortion, and there's not too much lost if it goes wrong because it's faulty anyway. So it makes a good test piece to learn on.

Remove and re-fit it a few times until you're happy with what you're doing. Then, if you haven't spotted the fault already, swap with one of the others, That will narrow things down further - does the fault stay with the balance or the cock?
 

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Discussion Starter #13
That's what I suspected when I re-read the first post for clues, and there's nothing wrong with that - far better to be aware of your limitations than dive in head first like we've seen some do on here then be posting about "does anyone know how to rebuild this mangled part?" :D

In this case, though, it may be time to take a deep breath and the next step by removing the balance from the cock / bridge (technically cock if it's only supported at one end btw). You'll really need to do that anyway to the faulty one to be able to inspect the top pivot properly without risking hairspring distortion, and there's not too much lost if it goes wrong because it's faulty anyway. So it makes a good test piece to learn on.

Remove and re-fit it a few times until you're happy with what you're doing. Then, if you haven't spotted the fault already, swap with one of the others, That will narrow things down further - does the fault stay with the balance or the cock?
Fair point. I've fiddled with this balance for long enough at this point and now basically consider the whole piece a spare movement for parts for other watches, so I may as well take it to the next level, even if just for fun.

Thanks.
 
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