Hi all just started to wear my po8500 more regularly and about 2 days ago I realized that it was running around 30 mins fast so set the time correctly and just looked again and it's 15 mins fast in just 2 days....the watch is around 2 years old so shouldn't need a service yet...Is this something that omega would put right?

 

I'm no expert in these kind of things, but if you work or are near electronic equipment with your watch, it might be magnetized.

 

Magnetism would be the first thing with gains like this, but in this specific case the possibility of this being the problem would depend on what version of the 8500 movement is in your watch. If it is prior to the silicon balance spring, then yes it could be magnetized and causing this gain. If it has the silicon balance spring, then this is not likely to be the issue.

If you PM me the serial number of the watch, I'll see what version of the movement it has.

Can I ask if the hands line up properly when you set the watch to 12? The 8500 watches also have a hand fitting issue and the hands might be drifting, but then you would see a misalignment so the hour and minute hands would not hit the marks properly.

Cheers, Al

 

Thanks...the hands line up perfectly at 12 & i believe that it has the silicone balance spring,on the back it has si14 .
I'll pm you the serial number

 

First I hear of the 8500 having issues. I thought it was bullet proof

 

Can you think of any shocks that the watch might have sustained? Sharp knock against a wall? Drop? Definitely sounds like a hairspring/balance issue given that the change was sudden. It would take one heck of a magnetic field to magnetize a modern watch.

 

When you find the problem, keep us informed. I'm very curious about the problem / solution.

 

I'm interested to hear what the problem is. I have a seiko i wear to work (I'm an electrician) and I do a lot of high voltage work which puts me near some series magnetic fields and even it has never become magnetized.

 

The watch kept perfect time last night.. Worn it today for around 4 hours and it has gained just over a minute..
No no knocks /drops etc
I'll keep an eye on it today

 

It has now gained around 5 mins in 7 hours

 

Based on the Si14 marking on it then it has the silicon balance, and the serial number you PM's me also indicates it's a B version with the silicon balance, so not likely magnetism.

If I understand you last post, it ran fine when sitting overnight but runs fast when worn, is that correct? If so, that could be the watch knocking. This is where the balance amplitude is too high when the watch is fully wound, so the balance wheel swings around too far and hits the pallet fork, and then bounces back quickly, and this increases the rate dramatically. I've never seen this happen on a co-axial watch though...

If this is the case, it's likely due to some issue in the one of the mainspring barrels, and it is letting too much power get to the escapement. Sometimes too much braking grease in the barrel can cause this, or if say on a vintage watch, someone has installed a mainspring that is too strong. On the 8500 it could be the barrel design issue that Omega has identified, but I'm not clear that this would result in knocking.

Some people call this overbanking, and another term for it is galloping, because on a Swiss lever watch, it sounds a bit like a horse galloping when this happens. You can simulate this on a manual wind watch by winding it until it's fully wound, then turning and holding the crown to apply even more power to the wheel train. I did this a while ago on a cheap movement I had in the shop to show what this sounds like:

So as I turn the crown you can see the ratchet and crown wheel turn, and then you can hear the watch start to knock, until I let the power off by releasing the crown. By the way, this is why the crown turns backwards on manual winding watches when you wind - the click allows the ratchet wheel to back up slightly so you don't cause this very problem when you get to a fully wound state.

Now no one can say for sure what the problem is with your watch, but this is just one possibility. It obviously needs to be sent in to be looked at.

Cheers, Al

 

Yes when I listen it sounds like it's galloping.. It doesn't sound very good at all..
Al thank you for the detailed information
I'll be putting it into omega next week

 

just a little update
Omega have had the watch for a week or so and the report says....complete service category 1
Barrel 2 complete
does this mean that they have replaced the no2 barrel ?
and are going to give it a full service
also they have estimated that i will have the the watch back in around 2 weeks is this enough time to service a watch.

must say that the service from Omega has been absolutley outstanding so far

 

Yes, it means they replaced the entire #2 barrel - so this includes the barrel drum and cover, barrel arbor, and mainspring. This is the barrel that is the automatic barrel with the slipping mainspring - this fits with my theory of knocking I stated above. Most likely the slipping of the spring was not happening soon enough, building too much tension in the spring, and causing the knocking.

Cheers, Al

 

Thanks for the reply Al
so is this a known issue with the co-axlial movement or more likely to be a one off problem

 

Could be a common issue on these or not - I have no idea.

 

Would the pivot premature wear issue you mentioned as a possible cause of the increased rate (10 sec/day) I observed with my AT 15'000 Gauss also lead to this type of Knock? I've listened to my AT 15'000 Gauss after a 45 min swim, but I could not detect the galloping sound. However, if it's sporadic, I might not "catch it in the act". Magnetized watches show the same sporadic acceleration due to a different cause (spring coils touching). I've caught a magnetized watch in the act of accelerating before, but that watch was much faster than 10 sec/day.

 

No - rebanking is a mainspring and power issue, and worn balance pivots won't affect this.