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Zenith 120 train wheels


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Zenith 120

Hi,
I have just serviced a Zenith 120, with centre second hand. The problem is, when all the train wheels are in place and all other parts, barrel, keyless and motion works. The watch will wind and run, but when the crown is pulled to change the time, the train wheels lock up totally. Is this something to do with the Hack feature, or have I assembled it wrong, perhaps two pinions are opposing each other.. 
I have been servicing for 4 yrs and have not come across this before. The third wheel has the double pinion. 
If anyone has a service schedule for the 120, or has a solution, I would greatly appreciate the help.
Keith
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yes it does and holds tight. If I take the pressure off slightly with an oiler it allows you to rotate the hand wheels, but in only one direction.

There is something in opposition somewhere. 

I cannot be the only one to encounter this problem, surely. :(

Edited by Legarm
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Sorted it. The intermediate drive wheel for the minute cog is meant to be a friction fit enabling it to rotate. Some one had crimped it on so hard, it wouldn't turn. Stripped it an reamed it out slightly. Now working a treat.

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Sorted it. The intermediate drive wheel for the minute cog is meant to be a friction fit enabling it to rotate. Some one had crimped it on so hard, it wouldn't turn. Stripped it an reamed it out slightly. Now working a treat.

Never worked on a Zentith movement. But sounds like you found the problem. Is it like on some Omega movement that has a cannon pinion on the third wheel? 

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Never worked on a Zentith movement. But sounds like you found the problem. Is it like on some Omega movement that has a cannon pinion on the third wheel? 

I have worked on a few Zeniths, but not one with this type.

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