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mzinski

Adventures in Servicing a Gen Omega Seamaster 1120 Movement

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mzinski

After having serviced 3 genuine vintage Tudor movements, a couple Sellita’s, and numerous Asian clones, I’ve decided to embark on the journey to service a genuine Omega 1120 for a Seamaster. 

Received the watch, looks good albeit clearly worn and loved. 

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I give it a full wind, set the date, set the time, and...nothing. It’s not ticking. Some more winding, some gentle shakes...nothing. I flip it upside down...there it goes. Hmm, this doesn’t bode well. But I’ll reserve judgement until it’s been torn down and cleaned.

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On to removing the bracelet, caseback, and dust cover. 
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Looks pretty clean except the stem is fully rusted and the movement ring is rusted in to place. I hope not to discover anything bad when I get the dial off. 

Off comes the automatic works and rotor together since the rotor screws are on the underside of the automatic works. 

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Now to remove the movement, take off the hands, and dismount the dial. It takes a bit of careful effort but the rusted movement ring releases. Hands are set to be stacked, protective Mylar cover over the dial to protect dial, Saran Wrap over hands to protect finish on hands. I like to use the pry bars in lieu of the hand removing tool, I have more control. 

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Next I flip the movement back over and remove the balance, gear train c0ck, and barrel bridge. 

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Back to the top side. Thankfully no further rust or corrosion has presented itself. Off comes the date wheel, calendar works, wheels, pinions, and finish up with the keyless works. 

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Main plate stripped. Automatic works and barrel bridge stripped down. Everything is neatly organized and ready for a four stage ultrasonic cleaning and rinse. And then it’ll all come back together with a bit of oil. 

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Since the balance wheel, pinion, and jewels look to be in fine shape I hope the lack of consistent movement is simply grime and age. 

Stay tuned. 

@FoxWilde

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fatarms

Good luck, my friend.  You have bigger balls than I do when it comes to gen movements.

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Theviking

Great work @mzinski

And thank you for documenting it. 

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FoxWilde

;D 

so exciting

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BM284

This is fantastic - I can live through my ‘want to be’ watchsmithing vicariously though your threads! Looking forward to the re-assembling of the movement :thumbsup: 

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FromRussiaWithLove

Good work, thanks for sharing. Subscribed!

What I cannot work out is how you can do all is this so easily, yet you didn't know how to get that rotor off the other week. Is that because you've always worked on Gens before and you're just getting used to the sneaky, fake screws, glued-on method of the reps?

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mzinski
5 hours ago, TomatoheadFred said:

What I cannot work out is how you can do all is this so easily, yet you didn't know how to get that rotor off the other week. Is that because you've always worked on Gens before and you're just getting used to the sneaky, fake screws, glued-on method of the reps?

Ha! Right?! 

I’ve found that gen movements are much easier to work on compared with reps, clones, and oddball assemblies because they are better constructed, more thoroughly documented, and don’t use tricks to make them look what they aren’t. And then there’s me still learning - I don’t know what I don’t know. Having worked predominantly on ETA’s, I’ve become accustomed to screwed on rotors (topside and underside). That other Omega chrono movement taught me rotors can have special screws that require a special tool - because why not make something more complicated, right? 

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GenTLe

I've gone now through many different services, from Seiko to Miyota, all the ETA clones used in reps and 7750s too.

Still I'd be very afraid to put my hands into a gen movement from another person's watch... Even if, like in this case, that's nothing else than a basic 2892 Eta.

Consider the possibility to change the mainspring as this may be set (you'll check once removed it from the barrel).

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mzinski

Cleaned and ready for reassembly - mostly. 

After four ultrasonic bathes (1 cleaner and 3 rinses) all the parts were heat dried and organized, inspected, and prepared for reassembly. Also decided to demagnetized for good measure. 

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Balance wheel and bridge got a One Dip bath instead. 

Upon inspecting the balance wheel I noticed the Hairspring had a bit of a kink and was touching. Maybe this explains some of the issues it was having earlier.

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If you look closely you can see the pin kinks in towards the center and is crooked. 

Anyways, I think most normal people would opt to buy a new balance wheel for $50. Not me! I decided to attempt to reshape the Hairspring. 

No easy feat, I will admit. First the Hairspring must be removed from the wheel - a pair of pry bars work well. It’s very similar to removing a hand set but smaller and more fragile. This was done without issue. 

Next on to reshaping the Hairspring. Using two pair of tweezers, one must incrementally, patiently, and carefully grab the spring where it is out of shape and basically massage it back to position. To confirm my reshaping I would lay the Hairspring centered on the bridge, frequently. 

Fast forward about 60 minutes and I have a center, flat, and well shaped Hairspring. Yay! 
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Last step is to press the Hairspring collar back on to the balance wheel. Pro tip, remember to mark the orientation of the spring before removing so it can be replaced correctly. Well, I wish I were ending this story with a pretty picture of a balance wheel complete...but I’m not. In pressing the collar something moved and pinched the spring. I don’t think I’m going to be able to reshape it this time. 

Lesson learned, just buy the balance wheel complete and install it! 

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Nikosaldente

I love watching these types of adventures!

It sucks that the hair hairspring got pinched while trying to put it back, but at least you managed to massage it back to shape!

Those 60 minutes add to your experience time...

Looking forward to seeing the rest!

Thanks for sharing!

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mzinski

While I’m waiting on some parts, good progress was made in the lubricating and reassembly of the movement. On order is a new balance wheel complete, stem, and crown. 

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Barrel bridge with integrated click comes together nicely. 
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Installed on to the main plate with the drive train. 
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Keyless works installed using the old stem. 
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Pallet fork back on. Tested for distribution to the fork, flicks back and forth nicely. 
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Automatic works. 
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Rotor screwed back on. Notice this one is screwed in from the underside. When doing anything to this movement, the whole automatic works needs to come off with the rotor attached. Not particularly convenient. 
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Date wheel, date jump, and pinnions installed. 

Look forward to getting the parts and regulating the movement. 

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