i recently brought a 1969 omega seamaster chronostop jumbo. I noticed condensation on inside of lens when cold so had it serviced. When I got it back the condensation issue had gone but it was running very fast and making a funny noise when being wound so I took it back to jeweller and was told I had overwound it and broken the mainspring. It cost me more money. Is this common?

 

Usually, the only way to overwind a watch is with a pair of pliers and King Kong strength. However, if the mainspring was rusted or weakened, it is possible to break it.

Now tell me why you don't have an avatar picture yet.

 

Not sure it takes that much strength. If you overwind a watch you can break the mainspring.

 

I will do the avatar later. The jeweller has asked me to go and see him to show me how to wind the watch properly. I think they missed that the mainspring needed replacing and it's easier to say it's my fault

 

I had a personal lesson in how to wind a watch from Roland Murphy after I unpacked my RGM 801 COE and immediately over wound it. Back it went. Wind till you feel resistance and back off two rotations.

 

"Back off two rotations?" How would that help? You simply cannot "back-wind", or un-wind a manual wind watch, by reversing the crown.

 

Chronostops use cal 865 right? If so, I think yes technically you can overwind a manual movement.

Automatic movements have a mechanism built into the main spring that prevents it from being overwound by the rotor.

 

Agree you cannot unwind. I think the point is to stop the user from over winding. That's what he told me to do and that's what I do. You can disagree with him but I wont.

 

RGM video ... Winding a manual watch.

 

Winding should be a smooth easy function. When getting to the end you feel the resistance and know to stop. Most likely they didn't change the mainspring and it just snapped due to age.

They should replace it for just the mainspring cost as it should have been checked in the first place.

DON

 

I've been to see the jeweller today and there was no charge for the mainspring and the watch is keeping perfect time now. I bought a new Hirsch strap for it which I will pit a photo on later

 

Over winding a watch is pretty much a watchmaking legend...

 

You can't over wind a watch.... Period.

 

I just watched the video - Roland isn't saying you can "unwind" a watch. To be very simple, he's talking about a quirk of the old Hamiltons and how to get the winding gears to set properly. Start watching at 1:00 for a few seconds where he talks about the 'click'.

 

It's not a quirk of old Hamiltons. To explain, he does mention the click in the video, which is a part of the winding system that keeps the mainspring from unwinding. Here is a video that shows the click in action on a manual winding ETA 6497 that I pulled out of a drawer to illustrate how it works:

You will note that as I wind the clicks single tooth slides past the teeth on the ratchet wheel. The ratchet wheel is in turn connected the barrel arbor, which is what you are turning in this case, and the arbor then winds the spring around itself inside the mainspring barrel. In this type of watch, it's the barrel that turns to release energy to the wheel train.

When I stop winding, you will notice the click moves back and allows the ratchet wheel to turn the other direction a few degrees. This is to ensure that at the very end of the wind, when the mainspring is fully wound, that excess tension is not generated on the spring if the user forces the winding one click too far on the ratchet wheel. If that happens at the full wind state, more torque can be applied to the wheel train than the watch was designed for, and this can cause excess balance amplitude and rebanking (or knocking) as I demonstrate in this video:

You can see the ratchet and crown wheels turn in the video frame, and note that they don't turn back because I'm holding that excess pressure on the crown. You can then hear the sound of the escapement change as the amplitude increases, and then the watch starts rebanking - this is where excess amplitude will cause the impulse pin (roller jewel) on the balance to come around so far that it strikes the outside of the fork horn, causing the balance to bounce back the other direction - this leads to a very fast rate.

What Roland is cautioning against is that if you wind right to the end, and the crown seal is so tight on the case tube that the crown can't back up when the click tries to unwind those few degrees (like me holding it in the second video), it could lead to a rebanking situation. Although this is not ideal and will cause the watch to run fast, it certainly not something that will damage the watch immediately, and the spring will run down eventually so the watch will stop rebanking when the amplitude drops.

What any of this has to do with the OP's situation? Not much I suspect. Mainsprings require more force that one thinks to break them outright, so either the spring wasn't replaced during service and was weak, or the new one had a fault (it does happen). Either way, not the fault of the owner doing anything incorrectly.

Cheers, Al