Longines Hydroconquest Calibre L633.5 (ETA 2824-2) Service

I have already featured several vintage Longines on the blog, so I thought I would write a post about the service of this “modern” Longines Hydroconquest. It is an Automatic Diver’s watch, powered by Longines’ calibre L633.5. As you will see, this movement is actually an ETA 2824-2.

The watch looks very smart indeed, and I am impressed by the build standard, it has a real quality feel to it. It came for a service. The crown was very stiff when winding or setting the time, so I will be investigating this as well.

Longines Hydroconquest Service Calibre L633.5

I start by removing the bracelet and opening the case back of the watch. This reveals the rather beautiful Calibre L633.5. As mentioned above, it is based on an ETA 2824-2 movement.

It is very nicely decorated, with a signed oscillating weight, and perlage finish of some of the components.

It very quickly becomes obvious that I am the first to work on this watch since it left the factory. I quite like that, as it is the opportunity to see how the movements are assembled in the factory, torque on the screws, lubrication etc…Longines-L633.5-ETA-2824-2

I remove the oscillating weight.Longines-Calibre-L633.5

I then de-case the movement. At this stage, I try to operate the crown/ stem, and it is working just as expected. The “stiffness” is gone, which confirms that the issue is not movement related. After further investigation, I find that the gasket inside the pendant tube is very dry, and with a bit of lubrication the issue is resolved.

After carefully removing the dial and hands, I can start stripping down the dial side of the movement.



Hour wheel, date indicator, minute train bridge and date jumper maintaining plate can come off.






I proceed further with the removal of the cannon pinion / driving wheel, minute wheel, date indicator driving wheel.






I release the incabloc spring to remove the cap jewel and its setting.






That’s the dial side completely stripped down.





I move on to the other side. On this photo I have already removed the automatic works, exposing the rest of the movement.





I strip the automatic works




The ratchet wheel, crown wheel and barrel bridge are disassembled.




The barrel comes out.





And the movement is now fully disassembled, ready for cleaning and inspection.Longines-Hydroconquest-Service-Disassembled




I reassemble the mainspring after applying the correct lubrication. This is critical to achieve the required power reserve.




I then lubricate the cap jewels.

I install the intermediate wheel, barrel assembly and bridge.




I now install the keyless work.






I build up the train.





As I install the escapement, I notice that the pallet jewels are not clean, despite having been through the usual regime of watch part cleaning solution in ultrasonic and two stage rinse, all 3 stages carried out ultrasonically. They should be spotless, so I clean them manually.

Much better now (what you can see now is only shellac, the compound fixing the jewels to the pallet fork).




I can proceed with installing the pallet fork.





I then fit the balance wheel, wind the watch and regulate it, and rebuild the automatic works.



I then move to the dial side again.





And complete the assembly of the movement.

The watch is re-cased, the oscillating weight installed. 

I do not typically show timegrapher readings after a service as they are quite meaningless out of context, but I decided to include this one as I happened to have it on file. This is the kind of reading that I like to see for that movement, with a good amplitude, no beat error, and a very stable rate.

The gaskets are lubricated, and the watch is now ready for a wet pressure test, which was passed with flying colours as expected. 

The watch is now ready for a couple more years of reliable service. 

4 Replies to “Longines Hydroconquest Calibre L633.5 (ETA 2824-2) Service”

  1. I really like the way you show the details of your beautiful work.
    Is the 2824 top grade? or elabore?

    Is the shape of the balance wheel spokes straight?
    If so, it is Elaborae, if curved, Top I believe…

    Thank you in advance.

    1. Hi, thank you very much. Not sure about the grade, the balance looks like it has straight arms on the pics.

  2. I’m puzzled that the VPH is reading 28,800 whereas my Hydroconquest (2018) reads at 25,200 VPH.

    1. That would be because yours has a different movement, with a different frequency. Longines Cal L888.3 has a 25200bph frequency for example

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