First A7750 teardown and rebuild (with MANY pics)

[GenTLe 1,510]

Finally I received all the needed greases and a correct movement holder for hands setting, so I decided to try the tear-down and reassemble of the "demoniac beast": Asian 7750 (a new spare one)

 

Practically I'm following the ETA official oil chart, but in nearly the reverse order.

 

First the movement fully assembled (without dial and hands):

 

 

and without the day wheel. You can notice the wire-spring, that one is quite difficult to fit (already tried)...

You also see the 2 levers that move the date and day wheels, and understand why you should NOT change the day/date with the stem when they are engaged.

 

All the "clicks" of the day and date wheels are now gone, as like as the DDWs too:

 

Date plate removed.

Do you see that kind of "boomerang shaped" part near the center at h2? That's plastic, pure plastic.

 

Movement rotated and autowind bridge removed.

At hour 9 you can see the spring (straight line one) that prevent the main spring to be discharged through the autowind and counterweight

 

Another little step:

 

Chronograph bridge removed, at h12 there is the crown wheel and at h10 the ratchet wheel. Between h8 and h9, at the extreme left, the click spring.

 

Winding gears removed (look how they save on cote de geneve finiture where it's not visible...):

 

Barrel bridge gone too:

 

A detail of the balance:

 

Ready to remove the keyless :

 

PS: the only little drops of oil were in the keyless, all the gears were running totally dry...

[GenTLe 1,510]

Now the questions:

 

1) I can't remove the 2nd and 4th wheels of the gear train because there is the driving pinion which looks forced on the 2nd wheel pinion.

How can I solve this without bending the 2nd wheel Thanks to JSJ that pointed me to the ETA animation, I see that during assembly that little gear is pressed over the 2nd wheel and so I managed to remove it

 

See here:

 

 

2) I removed the "Operating lever spring" (nr. 35 in the pic below), but I already foresee problems in fitting it back because I can't see how it fits between the barrel bridge and the main plate. Any suggestion / special instruction?

 

3) Day and date drive wheels: on the ETA charts there are "arrows" to indicate how they should be fitted. Any more precise sign? Special instructions?

 

And finally: do you have some general suggestion? Something that I should carefully take care when reassembly?

 

Thanks!!

GenTLe

[JSJ 0]

Are you watching the animated version of the disassembly/assembly on the eta website mate? It gives proper animations of assembly too. If you are not, I'll dig the link out for you.

[JSJ 0]

Here it is http:// http://www.eta.ch/swisslab/7750/7750.html

[GenTLe 1,510]

Yeah! Thanks a lot JSJ, totally forgot about it!!

 

EDIT: gave a look at the animation right now: i followed the same steps (a part that they removed the balance and the pallet fork a bit earlier). Still stuck with damn second wheel Looked at reassembly animation: the little gear is pressed on the pinion. Managed to get it out

[JSJ 0]

Your teardown is fascinating! Looking forward to seeing the next steps. Thanks for posting.

[10:10 Watch Repair 1]

Now the questions:

 

1) I can't remove the 2nd and 4th wheels of the gear train because there is the driving pinion which looks forced on the 2nd wheel pinion.

How can I solve this without bending the 2nd wheel?

 

 

 

 

 

2) I removed the "Operating lever spring" (nr. 35 in the pic below), but I already foresee problems in fitting it back because I can't see how it fits between the barrel bridge and the main plate. Any suggestion / special instruction?

 

 

3) Day and date drive wheels: on the ETA charts there are "arrows" to indicate how they should be fitted. Any more precise sign? Special instructions?

 

 

And finally: do you have some general suggestion? Something that I should carefully take care when reassembly?

 

Thanks!!

GenTLe

1. You pry it with hands levers on each side. That's why the plate has notches on either side.

2. It fits. You'll see, there's a little play there.

3. On the Swiss there is a reference mark on the maniplate. Not on the A7750

[Edge22 0]

Your teardown is fascinating! Looking forward to seeing the next steps. Thanks for posting.

 

^^^^ What JSJ said! ^^^^

[10:10 Watch Repair 1]

You also see the 2 levers that move the date and day wheels, and understand why you should NOT change the day/date with the stem when they are engaged.

You're not looking very carefully then. On the Swiss movement the double corrector (above the keyless) has a little spring which allows it to clutch so the movement won't get damaged if you try to change the date between 10-2. That's not always executed so well on the Asian, so they changed the design of the date corrector wheel. If you look at it, it rotates so that it won't jam the date wheel in place.

[GenTLe 1,510]

Now the questions:

 

1) I can't remove the 2nd and 4th wheels of the gear train because there is the driving pinion which looks forced on the 2nd wheel pinion.

How can I solve this without bending the 2nd wheel?

 

 

 

 

 

2) I removed the "Operating lever spring" (nr. 35 in the pic below), but I already foresee problems in fitting it back because I can't see how it fits between the barrel bridge and the main plate. Any suggestion / special instruction?

 

 

3) Day and date drive wheels: on the ETA charts there are "arrows" to indicate how they should be fitted. Any more precise sign? Special instructions?

 

 

And finally: do you have some general suggestion? Something that I should carefully take care when reassembly?

 

Thanks!!

GenTLe

1. You pry it with hands levers on each side. That's why the plate has notches on either side.

2. It fits. You'll see, there's a little play there.

3. On the Swiss there is a reference mark on the maniplate. Not on the A7750

 

1. Mounted the plate on the movement holder and pushed the pinion (from the date wheel side) with a sharp ended tweezer: it came out

2. I'll see

3. [censored] them... Also looking the 2nd pic they look like assembled wrongly (I've seen that setting the time was only changing the date - not the day - at midnight)

 

Anyway I found this (from here: http://www.replica-watch.info/vb/showthread.php?t=135678) that should fit the case:

 

Thanks 10:10, always really supportive!

 

PS: today I also tried to unassemble grease and reassemble a spare 2824 main spring barrel: without the estrapade it's a disaster... I managed to broke the spring after 1 good hour or attempts... :(

[GenTLe 1,510]

You also see the 2 levers that move the date and day wheels, and understand why you should NOT change the day/date with the stem when they are engaged.

You're not looking very carefully then. On the Swiss movement the double corrector (above the keyless) has a little spring which allows it to clutch so the movement won't get damaged if you try to change the date between 10-2. That's not always executed so well on the Asian, so they changed the design of the date corrector wheel. If you look at it, it rotates so that it won't jam the date wheel in place.

 

Uhm, I replaced a broken asian double corrector with a gen one... Didn't notice differences :-?

[SSTEEL 0]

You seem to be doing quite well thus far, keep up the good work mate, you can do it. I find the only tricky part of reassembly is the oscillating pinion, and I find lifting the movement holder up at one side slight aids the reinstallation.

[10:10 Watch Repair 1]

You also see the 2 levers that move the date and day wheels, and understand why you should NOT change the day/date with the stem when they are engaged.

You're not looking very carefully then. On the Swiss movement the double corrector (above the keyless) has a little spring which allows it to clutch so the movement won't get damaged if you try to change the date between 10-2. That's not always executed so well on the Asian, so they changed the design of the date corrector wheel. If you look at it, it rotates so that it won't jam the date wheel in place.

 

Uhm, I replaced a broken asian double corrector with a gen one... Didn't notice differences :-?

under the calendar plate. Some Asians have the spring, some don't. It's rarely done well enough that the double corrector will properly clutch.

[JSJ 0]

You also see the 2 levers that move the date and day wheels, and understand why you should NOT change the day/date with the stem when they are engaged.

You're not looking very carefully then. On the Swiss movement the double corrector (above the keyless) has a little spring which allows it to clutch so the movement won't get damaged if you try to change the date between 10-2. That's not always executed so well on the Asian, so they changed the design of the date corrector wheel. If you look at it, it rotates so that it won't jam the date wheel in place.

 

Uhm, I replaced a broken asian double corrector with a gen one... Didn't notice differences :-?

under the calendar plate. Some Asians have the spring, some don't. It's rarely done well enough that the double corrector will properly clutch.

Fascinating info Chris. Is it possible to buy the spring and retrofit to the Asian?

[10:10 Watch Repair 1]

 

Fascinating info Chris. Is it possible to buy the spring and retrofit to the Asian?

 

You know, I have never looked that closely. I don't think the part is available from ETA though.

It really doesn't matter because the date drive wheel has a different design.

At one point I posted a video, maybe GenTLe would like to try changing the date with time between 10-12 and video the results.

You'll see the date wheel spin eliminating the problem, or, if you jam the wheel (or have one with the old or Swiss design) you can see the double corrector clutch (or try to.)

[Irishcain 0]

Great stuff. Keep posting!

[JSJ 0]

 

Fascinating info Chris. Is it possible to buy the spring and retrofit to the Asian?

 

You know, I have never looked that closely. I don't think the part is available from ETA though.

It really doesn't matter because the date drive wheel has a different design.

At one point I posted a video, maybe GenTLe would like to try changing the date with time between 10-12 and video the results.

You'll see the date wheel spin eliminating the problem, or, if you jam the wheel (or have one with the old or Swiss design) you can see the double corrector clutch (or try to.)

Thanks for that. Maybe I'll just keep avoiding the date change at the wrong time.

[GenTLe 1,510]

 

Fascinating info Chris. Is it possible to buy the spring and retrofit to the Asian?

 

You know, I have never looked that closely. I don't think the part is available from ETA though.

It really doesn't matter because the date drive wheel has a different design.

At one point I posted a video, maybe GenTLe would like to try changing the date with time between 10-12 and video the results.

You'll see the date wheel spin eliminating the problem, or, if you jam the wheel (or have one with the old or Swiss design) you can see the double corrector clutch (or try to.)

Thanks for that. Maybe I'll just keep avoiding the date change at the wrong time.

Considering how delicate is the Chinese double corrector, I'd follow this precaution:)

[joshc220 0]

I just did surgery on my 7750 sec at 6 chrono this week. I had trouble with the little spring and I actually opened it up a tad bit to make it easier to put on. This thing is insane for a first time try at repairing. I spent 12 hours working to get it running again and managed to snap off a couple of the post that run the small hands. Would be great if there were a place to get spare parts.

[JSJ 0]

I just did surgery on my 7750 sec at 6 chrono this week. I had trouble with the little spring and I actually opened it up a tad bit to make it easier to put on. This thing is insane for a first time try at repairing. I spent 12 hours working to get it running again and managed to snap off a couple of the post that run the small hands. Would be great if there were a place to get spare parts.

Buy a new movement then you'll have some spares. Unfortunately not spares of the IWC secs@6 module because I've never found anywhere to buy one. The Daytona movement is available though.

[AstroAvia 0]

When reassembling the watch, be careful with the escape wheel and its capilar posts. They are very easy to break when fitting the second plate, because there are so many posts to fit simultaneously one can easily miss the jewels and break the posts.

 

My personal difficulties have always been: breaking escape wheel's posts, reassembling the chrono hours counter gears/springs, fitting the oscilating pinion (in decreasing dificulty order).

[BC1221 44]

youre a brave man.

lookin good so far though. i wouldnt have the guts to attempt this.

i get scared a little any time i have to work on a 2813.

[joshc220 0]

I just did surgery on my 7750 sec at 6 chrono this week. I had trouble with the little spring and I actually opened it up a tad bit to make it easier to put on. This thing is insane for a first time try at repairing. I spent 12 hours working to get it running again and managed to snap off a couple of the post that run the small hands. Would be great if there were a place to get spare parts.

Buy a new movement then you'll have some spares. Unfortunately not spares of the IWC secs@6 module because I've never found anywhere to buy one. The Daytona movement is available though.

 

Where would one go about finding a replacement daytona movement?

[GenTLe 1,510]

 

 

Where would one go about finding a replacement daytona movement?

 

If it is one of those with running sec at 9, hours at 6 and 30 mins at 3, it should just be a modified 7750 (you can find it on the bay, sometimes sold as 7753, which it isn't in reality) or a real 7753 (which has a quick date set pusher at 10, not used in the daytona).

[joshc220 0]

Where would one go about finding a replacement daytona movement?

 

If it is one of those with running sec at 9, hours at 6 and 30 mins at 3, it should just be a modified 7750 (you can find it on the bay, sometimes sold as 7753, which it isn't in reality) or a real 7753 (which has a quick date set pusher at 10, not used in the daytona).

 

mine is one of the lucky seconds at 6 models