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A7750 (9-6-3) Service Walkthrough - lots of pictures

ngy

You're Saying I Can Sell?
31/10/17
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This is yet another A7750 walkthrough. I posted this because a lot of the walkthroughs I was going through had broken picture links to photobucket, so I thought this may help those who are interested.

I was originally reviewing my Omega Speedmaster Racing 326-30-40-50-01-001, and servicing the movement, but I couldn't figure out how to change the title/move the thread, so I'm posting it here.

https://forum.replica-watch.info/for...0-40-50-01-001

Hope this helps!

Hey all, just posting a review of my first rep purchased from ChazingTime, the Omega Speedmaster Racing (https://chazingtime.co/product/speed...-rubber-strap/)

First off, ChazingTime has been amazing, very responsive and after 2 QC picture exchanges, was able to send me the watch, and it arrived very quickly.

On to the watch. this is the rep of the Omega Speedmaster Racing 40mm 326.30.40.50.01.001 (https://www.omegawatches.com/watches...2630405001001/). At casual glance, it looks like the real deal. I was looking for a 40mm automatic chornograph, and this one definitely fits the bill. The thickness is about 1mm larger than the gen, but it doesn't feel overly large (I have small 6.5" wrists).

Shot of the front and bracelet. The bracelet is usually where the most tells are, while everything is solid, not folded steel, the SEL have rather large holes in them for the spring bars, so it has a bit of play in it. The width is 19mm as per gen. The buckle exterior finish is nice, but once you open it, the finish on the inside is rough, and not refined. But it has considerable heft.

IMG_20171123_004808.jpg
IMG_20171123_004930.jpg



Side view, nice brushing on the case, good contrast to the polished beveled lugs:
IMG_20171123_004952.jpg



First tell: No date advance button at 10 o clock, date change happens at the crown (I prefer this anyway):
IMG_20171123_005002.jpg





Case back, amazing detail on the speedmaster logo, the engravings, Omega logo, Si14, Column Wheel, Racing and 'serial number' Another tell here: the serial number is upside down, but without gen, you wouldn't know.
IMG_20171123_005109.jpg


On the front, the slightly domed sapphire crystal has no AR coating. The bezel has an aluminum ring with the tachymetre printed on. Onto the dial: Nice layering, all indices are nicely applied/printed on. The subdials (sec@9, hr@6, 30min@3) all have the 'Clous de Paris' textured pattern applied, though not as obvious/pronounced as the gen. They are also on a lower layer as per gen. 'Swiss Made' font is small, accurate, and defined. Very sharp printing. Biggest tell here is the date window, which is sadly sunken due to the additional complication to move the dials from the original A7750 location (12-9-6 to 9-6-3).
IMG_20171123_005327.jpg


See the layering on the dial. Top where the indices are have a nice vertical 'brushed' look and white indices applied, and the lower layer has the 'Clous de Paris' texture for the subdials and the second indices along the perimeter.
IMG_20171123_005338.jpg


Mandatory wrist shot! Not too big for my wrist.
IMG_20171123_005437.jpg


Chronometer: Being the cam system in a 7750, the 'start' press requires some force, you would never activate it by accident. All dials work as per genuine. 'Stop' press is a little smoother, and the 'reset' requires the least amount of force. However, you do need to press the 'reset' all the way to reset the hour hand. Otherwise it can click, reset the second and minute hands, but the hour hand could still be skewed slightly. I've had a chance to play with a gen moonwatch, and it had the same feel.

Time keeping: So far, the one I received is quite satisfactory on my timegrapher, it goes up to +7sec, and -4 sec, dial up position, with 42 hour reserve. However, the movement is running dry, so I will need to disassemble and clean/lube everything.

Please ask me if you have any questions. Next post will show the movement, and I will have a write up with the disassembly and service of the A7750.
 
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ngy

You're Saying I Can Sell?
31/10/17
35
18
8
Also, came with a rubber strap. On the exterior, it looks nice, but open the clasp and...

IMG_20171123_160106.jpg


... you see the world's biggest tell, 'OMEGA' etched on. Really ugly, but not visible normally. The rubber is flexible, and it works relatively well, but I'm not a big fan of it.
IMG_20171123_160126.jpg


Better shot at the caseback.
IMG_20171123_011513.jpg


And revealing the A7750. The movement is dry, and fingerprints are left everywhere. Some hair, dust bunnies, the usual. Service is required.

IMG_20171123_155701.jpg

IMG_20171123_155644.jpg

IMG_20171123_155631.jpg

IMG_20171123_155721.jpg





I'll post a write up here when I clean, lube and service the A7750. Stay tuned.
 
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ngy

You're Saying I Can Sell?
31/10/17
35
18
8
Alright! Finally found some time to service my new toy.

A quick background, I'm NOT a watchmaker, I'm a mechanical engineer by profession, doing product design work during the day. Working on watches is my hobby, so I'm more of a watch enthusiast/tinkerer. I've serviced all my mechanical watches, albeit they have all been automatic non-chronograph watches to this point. This will be my first chronograph (and asian) watch I'm servicing. So please don't follow what I do, and please provide feedback if you see me doing something wrong =). I have no formal training in watchmaking and horology. My teachers so far have been Seiko 7S26, Seiko NH25, Miyota 8245 and Miyota 9015, and of course UoYT (University of YouTube). They've taught me everything I know so far.

So let's get started!

I'll be following the ETA guide for disassembly / lubrication / assembly (https://www.eta.ch/swisslab/7750/7750.html), with a few exceptions where I'll use Molykote DX over HP1300 on the high pressure chrono arms/hammers/impact interfaces.
Moebius 9010 - escapement, balance, second wheel, reversing ratchet wheel, rotor
Moebius Synth-a-Lube HP1300 - barrel arbor, train wheels, hacking lever, crown wheel, yoke spring, chrono pivots, ratchet driving wheel
Moebius 9415 - exit pallet stone
Molykote DX - all chrono arm/cam/hammer interfaces, winding stem, keyless works, driver cannon pinion.
Tamiya Anti-Wear Grease - from my RC car hobby days, a very sticky grease, used in high pressure metal-metal contact (CV joints, and used in gear differentials to provide 'limited slip' feel). I used it previously in my automatic barrel walls, and gives good braking and results. Very similar to Kluber P125 in viscosity/stickiness, but I cannot say much more about it. It's worked for me thus far.
IMG_20171205_011113.jpg


Here it is, the Asian 7750 out of it's case:
IMG_20171204_185054.jpg


Chrono seconds, hour and minute hands removed with presto hand remover. Seconds, chrono hours, and chrono minute removed with hand levers. ziplock polybag with a slit used as dial protector.
IMG_20171204_185847.jpg


Dial removed by 'unlocking it' at the top and bottom. Here's the shot of the added complication to move the 30 min counter from 12 to 3. The gear at 12 has a 'cap' that is friction fit on to the 30 min counter. 3 gears added, all jeweled, with additional plate for the complication, thus the sunken date wheel.
IMG_20171204_190228.jpg


Date wheel, and jumper/spring/cover removed.
IMG_20171204_194356.jpg


Sorry for jumping steps, just removing things as per the service order. I'm taking pictures as I remember to. Calendar plate + 12-3 transfer plate removed. Reset hammer (reset arm removed), hour counter, date jumper gears revealed.
IMG_20171204_203422_01.jpg


Turn movement over, and removed the rotor, rotor plate, and reverse ratcheting gear. things are pretty dry in here. Also note this A7750 has a 'ETACHRON' regulator.... NOT. It's just a decoration. (edit: I am wrong, the regulator actually works!) This is the 28800 bph version by the way.
IMG_20171204_195253.jpg


60s clutch, 30min counter wheel, chrono seconds wheel, oscillating pinion, reduction wheel, minute counter jumper, chrono bridge, ratcheting driving wheel, chrono friction wheel, start/stop lever, lock, minute counter driving wheel, and operating spring lever removed. Operating lever spring orientation noted.
IMG_20171204_201541_01.jpg


Chrono heart cam, hammer cam jumper, balance complete, pallet bridge, and pallet fork removed. Before removing pallet bridge, make sure you let down any power in the barrel by moving the spring out of the way of the ratchet wheel, and SLOWLY let the crown slip in your fingers. Never let it just zip down.
IMG_20171204_202030.jpg


Ratchet wheel, wheel core, and crown wheel removed.
IMG_20171204_202411.jpg


The movement on this layer is REALLY oily, looks like some light oil splashed everywhere.


IMG_20171204_202644.jpg


Barrel and train wheel bridge removed.
 
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ngy

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31/10/17
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So once we get to here, the rest of the train wheel and barrel is removed, and we have a fully disassembled A7750!
IMG_20171204_205407.jpg

IMG_20171204_205412.jpg


Actually almost full disassembled, need take the barrel apart! A light film of oil was all over the barrel, and when I opened it, it looks like it was packed full. Lots of grit inside too. Picture here for orientation of the mainspring. Popped it open by pressing the arbor against the table and the cover popped off.
IMG_20171205_002303.jpg


And the mainspring is out!
IMG_20171205_002501.jpg


So everything will get a nice clean bath. I clean my parts in my cheapo ultrasonic cleaner, filled with water, and then tiny glass jars (4 jars does not hold everything, I had several runs, swapping parts) with 99.9% IPA solution to minimize waste. All parts got a 10 minute ultrasonic massage to shake loose the grime. The main plate, barrel, and mainspring got an extra 10 minutes (20 minutes total) cause it was exceptionally oily/gritty/dirty.
IMG_20171204_235552.jpg


Once cleaning was done, I set them back in my tray with lint-free (kim wipes) paper for drying. (not all parts are in this shot)
IMG_20171205_010320.jpg



Finally, once with everything cleaned, we can begin putting the thing back together and lubing it! Again, here are my oils and greases.
IMG_20171205_011113.jpg


Started by assembling the barrel. Barrel grease on the barrel wall, and I wiped a thin layer of oil on the mainspring using 9010. Then using gloves, I hand assembled it back into the barrel. It takes a few tries, but I managed.
IMG_20171205_013227.jpg


Barrel, escapement, train, and hacking lever, back in place (light coat of Molykote DX under the hacking lever)
IMG_20171205_014519.jpg


It was getting late, so I forgot to take a bunch of pictures. But assembly here was straightforward, put things back to where they belong. (I followed the ETA technical guide). Barrel and train bridge back on. Barrel arbor, crown wheel, and crown wheel core, lubed with HP1300.
IMG_20171205_020428.jpg


To be continued!
 

ngy

You're Saying I Can Sell?
31/10/17
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So to finish off the thread!

Installed the balance complete and off it went ticking! Installed the crown to hack it and continued installing the rest of the chronograph.
IMG_20171205_042736.jpg


The chronobridge was a PAIN to get right. Aligning the oscillating pinion with the clutch? Tough as people say, but doable with two fine tweezers. Putting reversing wheel against the spring? again tough, but doable. Installing the reset hammer? No problem. But installing the the automatic bridge, without moving and all the above out? Yeah that was annoying. The bridge has a axle that goes through the reduction wheel next to the reversing wheel, that just loves to poke around and move everything.
IMG_20171205_055243.jpg


But it can be done! Patience, steady hands, multiple tries, it was done. Oh don't forget to have the cam/hammer in the right position. I had mine off and had to redo it a few times. But is done!
IMG_20171205_153604.jpg


Now at this point, I got in the zone and forgot to take pictures of the rest (ETA suggests to install the rotor now, but I flipped the movement over and installed the date wheel, and 12-3 transfer plate first. Then I put the dial, hands, and the movement back in the case before installing the rotor. In the past I found that installing the rotor first is a huge annoyance as the movement no longer likes to sit still).

When I first got the watch it was running about +7sec/-4sec. Then I timegraphed and regulated to about +5sec/-3 sec, with it riding at +1sec in the crown down and face down position, and I'm happy. Now the watch is back on the wrist, fully serviced and ready to roll for the next 5ish years!
IMG_20180206_205803.jpg

IMG_20180207_235428.jpg


Thanks for reading and feel free to ask me questions!
 
Last edited:

peterpl

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Well done. Was this your first attempt at servicing any movement? Quite impressive. Everytime I try to service anything I just stuff up and get annoyed if I have to attempt things 4-5 times. LOL
 

ngy

You're Saying I Can Sell?
31/10/17
35
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not my first time servicing any movements, I've worked on the Seiko 7S26 first, and the NH35, and Miyota 8245 and 9015 before attempting the A7750.

Thanks for the kind words, yeah it gets frustrating, but just gotta be patient and have steady hands lol!
 
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p0pperini

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I’m unable to see the pic
I can see all the pics on my PC using Chrome.

Guess it must be related to what you're trying to view it on. Try a different browser.
 
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kennygconspiracy

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What an amazing write-up. Thank you for all your time and dedication!

Sent from my ONEPLUS A6003 using Tapatalk
 

mrsullivan

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Thank you guys for digging this up, very useful!

Envoyé de mon ELE-L29 en utilisant Tapatalk
 

p0pperini

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What an amazing write-up. Thank you for all your time and dedication!
Not entirely sure the OP is around to enjoy the compliments as the guide was posted two years ago. But I agree, it's a really good guide, and the OP also provided a handy link to the ETA Swisslab step-by-step diagrams which are excellent too.
 
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Teenyweeny

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Yes I can see the pic via browser now
Agreed it’s an amazing article


Sent from my iPhone using Tapatalk
 

ngy

You're Saying I Can Sell?
31/10/17
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Still around here and there! Glad you guys appreciate the posts! Pics are still up!
 
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