Longines L650.2 - Dubois Depraz Chrono

​In the workshop this month is this Longines Conquest chronograph featuring a Dubois Depraz Chrono module. Sent in after having stopped it was time to finally service this watch and get it back in running order, having removed the back it was visible the hack had somehow come out of its place and was stopping the balance.

With the back off it is clear the casing needs a clean to get rid of the debris that has built up. Dirt/Debris and fine movements do not play well together so an ultrasonic clean should remove this problem. This watch is front loaded so the front bezel will have to come off to release the movement.
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With the movement now free we can remove the dial and hands and take a look at the movement and the module that sits on top which comprises the clever chronograph assembly.

Unlike other chronographs the module design used here is very clever, by using the power of the main movement to power the module you can service the main movement separately without needing to disassemble the whole watch. The module is designed by the famous Dubois Depraz and it sits neatly on top of the main movement ( ETA 2894-2 ), this is just one module design of the many specialist designs produced by Dubois Depraz. A large amount of popular Swiss brands turn to Dubois Depraz for their chronograph needs ( including Rolex ), no doubt this in turn saves a lot of headaches and money in r&d, why build something from scratch when there are specialists who can do it for you :)
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The module above is secured in place by three screws and simply lifts off the main movement, no fuss or special tools just lifts right off. The beauty of this design is that you don't actually have to remove the dial & hands as the whole unit is not directly connected to the main movement ( the train wheels etc ). Instead communication is via small transmission wheels which pass the required ratios through intermediate gears. However in this case the date wheel is out of sync so adjustments must be made to the upper chrono module. The module itself is not serviced and instead it is recommended to be replaced outright ( at rather large cost ), however this module is in pretty good shape so not much needs doing here.
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Stripping down the main movement can be done just like any other ETA 289X movement, simple and straightforward unlike other chronographs. Only a few photos taken below as this is going over old ground.

With the movement cleaned, assembled and lubricated it was then tested for several days for timing before being finally adjusted and then recased. The casing had gone through the ultrasonic removing all the gunk and debris and even bringing back some sparkle to the diamonds around the bezel, the glass was also given a light polish to remove the scratches and make the dial more visible.
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Movement fully assembled

Dial fastened in place

Hands fitted :)

Front loading case design

Secured in the casing

Ladies watches are often thought of as small little things that our grandma might wear so its refreshing to see a nicely sized piece with all the bells and whistles :) A lovely watch returned to good running order and no doubt a happy customer :)

More blogs to come but bare with me as it has become busy season and time is limited :)
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