Omega 2500B coaxial question - not running after replacing broken pallet fork

[Dmitry]

A friend asked me to look at a non-running omega 2500B. Whenever the crown was pushed in, hands were moving like crazy. I suspected a broken pallet fork, which would release the train as soon as the hacking mechanism was deactivated by pushing the crown in.

I turned out to be right, upon inspection of the watch I found the top pivot of the pallet fork having a broken top pivot.

I have ordered a replacement, part 41000, which according to a few web sites would fit the 2500B movement:

https://www.ebay.ca/itm/256646900576

However, when I installed the new pallet fork, the geartrain is not advancing when I gently push the fork from one side to another, a typical check I would do for a regular pallet fork escapement with just a bit of a wind. 

I have not worked at coaxial escapements yet and wonder if this test is even applicable.

When I install the balance wheel, by putting it into the bottom pivot first and then rotating clockwise by about 90 degrees, I see the roller engaging with the three-teethed pallet fork, but it does not run, similar to a regular watch being overbanked, the balance wheel just locks. 

Can anyone please share their experience with this coaxial movement? Here are a few pictures.

Is the pallet fork part correct for this movement?

Is there a way to check proper escapement function before putting in the balance wheel?

Am I following the proper protocol for inserting of the balance wheel?

I have include a picture of both pallet forks, tth eone on the left is the old one with the broken pivot. They look identical.

Thank you.

[JohnR725]

2 hours ago, Dmitry said:

I have not worked at coaxial escapements yet and wonder if this test is even applicable.

I'm assuming that you have all technical documentation? Just in case I have PDFs attached that you may find helpful. In other words there is the service guide their something for checking the escapement and the instructions on lubrication cover the lubrication of the escapement which is critical. Lubrication isn't actually for lubrication my understanding is for a shock impact then if I was changing the pallet fork and probably change the escape wheel at the same time

Then is also the problem of Omega possibly upgrading things. But oftentimes upgrading is requiring several parts to be changed at the same time so they all work together. But we don't have new enough documentation for that so would be speculation on my part if I was replacing the pallet fork I would also replace the escape wheel at the same time. Also based on someone I know sent their coaxial in for servicing and the service center replaced both components. Of course they have an infinite supply of components to replace things with.

 

8649_WI_54_E.CHECKING THE CO-AXIAL ESCAPEMENT FUNCTIONSpdf cousins.pdf 4435_Omega 2500A,2500B,2500C,2500D cousins.pdf 8645_WI_40_rules for lubrication cousins.pdf

[Dmitry]

@JohnR725 - thank you very much for the tech sheets, these turned out to be very useful, especially the oiling chart and the ways to check the alignment. No wonder Mark in his video on the 2500 movement has stressed the importance of the oiling documentation.

It is based on these docs that I now think that the coaxial escapement wheel in this movement is off and might have contributed to why I have found a pallet fork with a broken pivot.

Here is a brief video of what I mean by balance wheel not moving as though it is overbanked, the middle stone on the pallet, which is supposed to work in sync with the stone on the balance wheel seems to be blocking the wheel regardless of position, hence escapement does not advance.

As suggested to replace in pairs, I am now looking for a coaxial wheel to replace as well. Since these wheels are different between all models of 2500 variants, I suspect someone has been playing with this movement before me and might have sourced wrong parts.

If there are any observations from the video, please let me know.

Video 1 - https://1drv.ms/v/s!ArG5E62RGctxjt9v-b1cwc-fDtqgsA?e=ZvLXhB

Video 2 - https://1drv.ms/v/s!ArG5E62RGctxjt9wOmCnNtTwXNxRQw?e=A2EgGa

[JohnR725]

Yes looking at the videos something is definitely not right.

20 hours ago, Dmitry said:

Since these wheels are different between all models of 2500 variants, I suspect someone has been playing with this movement before me and might have sourced wrong parts.

Do we have any history of this watch? In other words your friend gave it to you for repair where was the watch before you got it?.

[AndyGSi]

Are you sure it's a 2500B and was the new fork sealed when you got it as their looks to be some subtle differences in the photo.

[Dmitry]

Yes, the part number was correct as per references and came in  a sealed package. I don't have any history, my friend also got the watch already non running.