Zenith El Primero – Cal. 400

Posted By on Feb 11, 2016 | 0 comments

Zenith El Primero – Cal. 400 (aka 3019)

Martin came in several weeks ago and dropped off this Zenith El Primero and a Jaeger Le Coultre Chronomaster. This watch, however, needs a lot of attention. For starters, the crystal is heavily scratched. The case tube was previously worked on by another person who decided to put in a different screwdown case tube. Which is understandable because getting parts from Zenith is next to impossible. However, the new case tube was put in at an angle other than what it was suppose to be at. And, in doing that, put pressure on the stem, movement and crown. Also, when that case tube was inserted, that person bored a larger hole into the case in order for it to fit. Which means, next time when another case tube needs to be inserted, we have to find one with the same diameter and thread. And, obviously now, we’re not talking original parts, which is not ideal. Also, because the tube was not installed properly, this movement was taking in dirt, air, humidity, water and everything else that was being thrown at it. Hence, the patina the 3 and 6 o’clock patina.

But, I digress and it’s time to dig in and do some work.

Such a gorgeous looking fella!


Some serious polishing is also needed.

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I won’t say it πŸ™

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The Zenith Cal. 400 in all it’s glory πŸ™‚ Hello pretty

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Hmmm, gaining 90 seconds a day, I would say needs some attention. The beat error isn’t horrible, but, I hope to improve the amplitude and rate.


The cracked stem and crown, such a shame. Unfortunately, both of these needs to be replaced πŸ™

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The oscillating weight off, it’s time to take a look under the hood.

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With the movement out of the case, it’s time to remove the bezel with my new Bergeon bezel remover. I admit, that’s a very interesting bezel click spring. It works really well though.

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Just a case and bracelet pic


Such a gorgeous dial. It’s a shame about the subdials.

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Time to remove the hands.

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This is the dial side of the Cal. 400 movement.


Back to the bridge side, I immediately remove the balance so as to not damage it in any way.


I start by removing the chronograph control spring followed by the hammer spring,

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Followed by removing the column spring

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Next, I remove from the column wheel itself the reset to zero rocker followed by the chronograph bridge.

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I continue removing the chronograph parts

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Thank heavens for pictures, otherwise this would take me much longer to put together.


Time to turn over the movement to the dial side and continue dismantling the movement.


The date corrector

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These 3 screws hold the calendar disc in place

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More to come.


  1. Jaeger LeCoultre - Master Compressor - Cal.. 751 - Horlogerie Watchtyme Montreal - Watch Repair Service - […] Martin dropped off two of his prized watches, a Zenith El Primero and this fella. The Zenith needed a…

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