Omega Speedmaster Professional Chronograph Issue

If it was me I would get it serviced straight away.
That click when you hit start sounds quite loud also.

When you press the start button, several things are happening. One is that the reset hammer is lifting off the cams of the chronograph seconds and minutes wheel. The coupling yoke wheel is also moving to come into contact with the chronograph wheel to drive it. If the hammer or cams are magnetized, they won't release cleanly and can cause the hand to move around before the coupling yoke wheel makes contact, in particular when you press the start button slowly. This can also be caused by gummed up oil on the hammer or cams, but I would not expect that in a 4 year old watch.

So the first thing I would do is demagnetize the watch, so if you have a demagnetizer or can find a local watchmaker with one, give that a try before you send the watch in for service. The watch doesn't need to be opened for this.

Cheers, Al

No harm in doing it, even if you are not sure the watch is demagnetized.

So to back up a bit and simplify this a bit, think of any ferrous object as having a bunch of small magnets inside it. Every magnet has a North and a South Pole. If the small magnets inside the object have their poles all lined up in one direction, so all the North are pointing in one direction, they all "pull together" and the object is magnetized.

What demagnetizers do is subject the object and the little magnets inside, to an alternating magnetic field. If that field is strong enough, it causes the little magnets inside to swing back and forth 180 degrees as the current flips back and forth. Depending on where you are in the world that will be 50 or 60 Hz. The idea is that you want to get those magnets swinging back and forth in the strong field, and then slowly reduce the strength of the field. As the field doing this swinging gets weaker and weaker, the little magnets will stop their poles flipping in pretty random orientations, and in this sate the object is not magnetized.

So there are two common types of demagnetizers out there. One has a field that is a constant strength, and in order to gradually make the field weaker, you have to move the object away from the field slowly, while keeping that field on. So place the object near the demagnetizer, press the button to turn it on, and slowly move the object away as far as your arms will allow before you release the button. Note that if you put the item near the demag, press the button, leave the object there and let the button go, you have likely just aligned all those little poles, and the object will be magnetized.

The second type of demagnetizer (the kind I use) is called an instantaneous style. When I place a magnetized object on the unit and press the button, it starts an oscillating field that slowly decays on it's own over time (when I say slowly it's pretty much immediate in real time). So I don't have to move the object away from the demag unit. So just make sure what type you are getting, and use it appropriately.

Cheers, Al

Glad it worked out.

Cheers, Al

Just to clarify one thing - METAS watches include a bunch of parts designed to make them resistant to magnetism, but these are only timekeeping related parts. So the balance spring is made of silicon, the balance staff is made of an anti-magnetic material, as well as parts of the pallet for and co-axial wheel, and even the shock absorber springs for the jewels on the balance. However, every other parts in the watch is the same as what's in a normal watch, and that includes the chronograph parts on the METAS chronograph models.

So this same issue with magnetism between the hammer and cams can happened on a METAS chronograph. The only other difference is that the current calibers are vertical clutch chronographs for the 9900 series, so they don't operate in the same way as a horizontally coupled chronograph does. You won't see the symptoms of magnetism on these watches, but it will still be there if the watch is exposed to a magnetic field sufficient to magnetize it.

The interesting thing is the new 3861 movement. It operates the same way as the 1861, and is 15,000 gauss resistant, but there no indication that this includes the chronograph parts. So I can see this same magnetism problem cropping up on those as well, even though the timekeeping won't be affected. So METAS is really about timekeeping, and not about all functions on the watch.

Cheers, Al