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Discussion Starter #1
hi all,


I had to service an Orient M-Force (aka Beast) with the Cal 40N5A movement but no technical guides or references could be found anywhere.
After some careful planning I went ahead with the servicing, taking step-by-step photos along the way.
Will be posting the entire process here as a guide for anyone else who might need it in future.

First of all, a pic of the watch. A hefty 47mm case, lefty crown, automatic with hand wind, hacking and power reserve indicator.

IMG_9391.JPG
IMG_9392.JPG
 

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Discussion Starter #2
The 40N5A is based on the same architecture as the workhorse 46943, which is pretty robust and straightforward to work with.

On this side of the movement, they are practically identical:
IMG_9393.JPG



Under the dial, however, it's radically different, with an offset date dial, power reserve indicator post just above the "23", and date dial guard held in place by a single screw next to the centre post.
IMG_9395.JPG
 

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Hi, could you tell me please, does the power reserve have an epicyclic gear on the end of the barrel arbor, or is it driven from the edge of the barrel?
 

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Discussion Starter #4
Hi, could you tell me please, does the power reserve have an epicyclic gear on the end of the barrel arbor, or is it driven from the edge of the barrel?
Epicyclic... I'll come to that later on
 

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Discussion Starter #5 (Edited)
Removing the date dial guard and date dial itself reveals the date jumper, date driving wheel and quickset star:
IMG_9397.JPG


To remove the date mechanism plate, unscrew the date jumper, another small screw to the right of the date driving wheel, and a bigger screw to the right of the power reserve indicator post. Under the plate you get the typical keyless works and date mechanism, plus the top wheel of the power reserve indicator engaging a small cog protruding through the plate, which is actually attached to the end of the barrel arbor:
IMG_9400.JPG


With the hour wheel, cannon pinion, intermediate setting wheel and power indicator assembly removed. You can see part of the power reserve indicator intermediate wheel through the cutout in the recess where the power indicator assembly sits:
IMG_9401.JPG
 

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Discussion Starter #6 (Edited)
I will cover the power reserve indicator later, during the re-assembly phase.

Moving on to the other side of the movement, the oscillating weight, balance and pallet removed:
IMG_9402.JPG


Removing the autowind framework reveals the manual winding mechanism that turns the transmission wheel directly. There is a small tension spring that holds the manual winding wheel in place, be careful not to let it ping off.
IMG_9403.JPG


Under the autowind framework is the familiar magic lever system, borrowed from Seiko:
IMG_9404.JPG
 

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Discussion Starter #7 (Edited)
Removing the wheel train bridge you get a typical arrangement, plus the hack lever:
IMG_9406.JPG


Underside of the wheel train bridge:
IMG_9407.JPG


With the wheels and barrel removed we get to see the whole intermediate wheel for the power reserve indicator that we had a glimpse of earlier, located under the barrel itself (this wheel is fixed to the plate):
IMG_9408.JPG


Finally, with the centre wheel and bridge removed:
IMG_9415.JPG
 

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Discussion Starter #8 (Edited)
The re-assembly is straightforward until we get to the power reserve indicator. The indicator is driven by two cogs located at the bottom of the barrel, one attached to the barrel cap, and the other to the end of the barrel arbor, which we saw earlier protruding through the plate:

IMG_9410.JPG


On the other side of the movement, we have the epicyclic power reserve indicator assembly, consisting of 3 parts - the big sun wheel (and post for the power indicator hand), the small planet wheel, and the carrier wheel with the post for the planet wheel:
IMG_9427.JPG


Because the planet wheel meshes with the sun wheel first before mounting onto the post on the carrier wheel, it takes a bit of fiddling to fit everything together neatly into the top plate. You can't just drop the carrier wheel in first, followed by the planet wheel, then the sun wheel.

Here's a look at how the sun wheel and planet wheel mesh together:
IMG_9425.JPG


When setting the power indicator assembly, first ensure that there is absolutely no power wound into the mainspring. (The same applies when setting the power indicator hand at zero.)

Once the power indicator assembly is in place, re-assembly can be completed with the installation of the date mechanism.

And that's it!
 

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Discussion Starter #9
Also worth noting, the shock springs on the balance jewels have changed from the 3-prong version found in the 46943 to a 2-prong version.
IMG-9431.jpg
 

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Excellent write up, thanks for taking the time to do this!
 

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Discussion Starter #11
I have just installed a NH35/6 balance complete in a 40N5A and believe most of the other basic movement parts will also interchange.
 

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I have just installed a NH35/6 balance complete in a 40N5A and believe most of the other basic movement parts will also interchange.
I have Orient Triton which also used 40N5A movement and I was looking for a technical spec online and nothing is available. And by luck I found your thread which confirm that I can install the NH35 balance complete on the 40N5A.
Question. Where do you buy the NH35 balance complete. I found this on Ebay but the saler is from Netherland and I am in the USA.
Here is the part Brand New Seiko Genuine (SII) NH35/NH36 Complete Balance Wheel | eBay
 

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