Troubleshooting balance versus other parts of the movement

I don't know how much experience you have, so if I suggest something that you already know, that's why...

First off, before you worry about the balance on any watch, the rest of the watch must be gone through thoroughly, and any issues fixed. These could be anything from simple worn pivots on wheels, to cracked jewels. If the rest of the movement isn't in top shape, then messing around with the balance won't get you very far. I mention this because although it appears in this case your amplitude issue is with the balance area, often it's not there, and is a more fundamental problem in the movement.

For more information on general servicing, if you search for the title "Basic watchmaking tips" in this watchmaking forum, you will find a series of threads I've written with all kinds of basic information on things like cleaning, lubrication, etc.

The amplitude and rates you are giving, is this just measured in one position? If so, is that dial down?

So loss of amplitude at the balance can be from a number of things. The easy things are that the balance jewels are not properly cleaned, or there's too much or too little oil. On some calibers mixing up the upper and lower cap jewels can cause amplitude issues as well.

More serious things include wear on the cap jewels that looks like this:



The solution here is to replace the cap jewel with a new one. But often when the cap jewel has a divot worn in it, the end of the balance staff pivot will also be flattened, like this:





This can be repaired by rounding over the pivot on a Jacot tool:



So now the end is rounded:

But this is delicate work and not something most beginners would tackle.

Of course you could replace the entire balance staff, and one of those tips threads takes you through that process.

Basic watchmaking tips - replacing a balance staff | Omega Forums

This low amplitude could also be caused by the balance spring not being properly adjusted so that it is concentric and flat. So there's a lot to look at, and you just need to start eliminating them one by one.

Hope this helps.

Cheers, Al

I doubt that the hairspring being off centre is going to create massive variations in amplitude. In my opinion, the best way to adjust the hairspring so that is concentric is to remove the hairspring from the balance wheel, then fit the hairspring to the balance cock. Then by viewing the collet with the balance cock upside down, you’ll see whether it is concentric or not. I’ve uploaded a picture of a Hamilton 992B hairspring installed on the balance cock. This watch came to me after the owner (a locomotive engineer) returned it to the “watch inspector” that serviced it, three times because it was erratic. The “inspector” was unable to adjust the rate properly. You may notice that the hairspring collet is not centred over the hole jewel. After I adjusted the hairspring properly, and conditioned the watch, I returned to the owner. The rate settled down, and it was running within seconds per WEEK.

I'll ask again - what position are these amplitude numbers from?

Photos are a bit grainy but it doesn't look bad.

What I don't see there is enough of a concentricity issue to cause the sort of amplitude drop you are seeing. In a dial up or down position, the balance should be riding mostly on the end of the pivot, so if the spring is forcing the pivot into the side of the hole in the jewel, there will obviously be consequences. If the coils are really off, it forces the balance more to one side and pushes the side of the pivot hard in contact with the jewel - this causes more drag and a loss of amplitude.

What I can't see here is how flat the spring is when in place. If the spring is dished up it can again pout force on the pivot that shouldn't be there. If it is dished down it can contact the balance wheel itself, and that is an obvious problem.

He’s already indicated that the beat error is okay, so not an issue. By the way, this movement is equipped with a moveable stud carrier, so turning the collet is not needed to adjust beat error.