a7750 ratchet wheel driving wheel issue

[nofitstate 27]

So I've come across a problem on a7750 chronograph movement in that it doesn't self wind.

 

On close inspection of it and comparing it to another a7750 movement I have it seems that the ratchet wheel driving wheel is the problems as shown in the red box in this diagram

 

 

All of the auto winding gears seem to be functioning correctly and the teeth on the larger part of the ratchet wheel gear are all present, but it's not turning the larger silver gear with the 4 holes next to it. Anyway this leads me to believe that the smaller pinion gear that is part of the ratchet wheel must either be loose (I think they are pressed together) or broken.

 

Now I've done a small amount of work on watches since discovering reps. Such as dial and hand swaps, date wheel resetting and swaps, and I'm not to bad when using my hands, so I think I'm about ready to give this problem ago.

 

I've read a few online guides and discovered this very handy flash guide at disassembling a eta 7750 movement http://www.eta.ch/swisslab/7750/7750

 

So to anyone with experience with the a7750 movement is there any tricks or things that you think may come in handy to me?

 

Thanks!

[SSTEEL 0]

That silver gear (four holes) has a habit of the pinion coming loose, remove it, and make sure its pressed in correctly.

[10:10 Watch Repair 1]

 

So to anyone with experience with the a7750 movement is there any tricks or things that you think may come in handy to me?

 

Thanks!

You have to remove a lot of finicky parts to get to it. Good luck.

[nofitstate 27]

 

So to anyone with experience with the a7750 movement is there any tricks or things that you think may come in handy to me?

 

Thanks!

You have to remove a lot of finicky parts to get to it. Good luck.

 

and despite watching and reading a load of guides this afternoon, come Saturday I'll be swearing at them all!

[1littlegreen 1]

Micky and Chris have this one pegged....

 

The auto-wind bridge is the nightmare..many parts to align and a very steady hand to place and adjust it just so. Have done many and sometimes still get hung-up once in a great while. As Chris said, good luck and gallons of patience

[binatang 0]

The pinion is friction fitted to the Ratchet Wheel (1482).

It could be :-

1) Pinion has come free from the wheel.

2) The Wheel can no longer grip the pinion.

 

You will be an appropriate punch & a riveting stake to help fix both problems.

[nofitstate 27]

Thanks for the input. I've heard the auto wind bridge can be a nightmare!

 

Anyway I watched another full tear down and rebuild of 7750 movement last night and will continue to watch videos on how it's done till the day comes.

 

Hopefully my engineering background will be of some use here, otherwise expect to see me wailing like a baby on here sometime Saturday afternoon!

[SSTEEL 0]

Just take your time with it, and be patient. I find raising the 7750 movement/holder up one side about 3mm, this helps keep the 60sec pinion in place.

[1littlegreen 1]

I have found this guy invaluable when I was first starting out with these movements......there, now you all know my secret...

 

[SSTEEL 0]

I have found this guy invaluable when I was first starting out with these movements......there, now you all know my secret...

 

 

That's Mark, his forum is http://www.watchrepairtalk.com/user/1-watchrepairguy/

 

Really nice guy. He's not posted any new videos lately due to him building his new workshop.

[nofitstate 27]

I have found this guy invaluable when I was first starting out with these movements......there, now you all know my secret...

 

 

That's Mark, his forum is http://www.watchrepa...watchrepairguy/

 

Really nice guy. He's not posted any new videos lately due to him building his new workshop.

 

I found that video yesterday and is bar far the best guide I've seen yet. He makes it look easy!

[1littlegreen 1]

Agreed Micky, great guy and has lent a hand when he has been able to.

 

I'm always looking for more of his videos, but yes he is always swamped. Good reason too

[nofitstate 27]

OK..... so after a small schoolboy error in not realising that I need to remove a couple of the hands to get some of the gears at the back out I've now found the problem.

 

 

The pinion gear has broken a couple of teeth! So I understand that the eta equivalent pinion won't fit without modifying the pinion diameter, so does any one have a spare Asian one lying around they'd like to sell to me?

 

Right now I'm off to upgrade to VIP as without this site I think I'd be pretty stuck!

Edited August 30, 2014 by nofitstate

[DR3M3L 4]

OK..... so after a small schoolboy error in not realising that I need to remove a couple of the hands to get some of the gears at the back out I've now found the problem.

 

 

The pinion gear has broken a couple of teeth! So I understand that the eta equivalent pinion won't fit without modifying the pinion diameter, so does any one have a spare Asian one lying around they'd like to sell to me?

 

Right now I'm off to upgrade to VIP as without this site I think I'd be pretty stuck!

 

Send me a pic of the part, I've stock of almost every parts both Asian and Valjoux 7750 & 7753

[10:10 Watch Repair 1]

 

Send me a pic of the part, I've stock of almost every parts both Asian and Valjoux 7750 & 7753

 

So I've come across a problem on a7750 chronograph movement in that it doesn't self wind.

 

On close inspection of it and comparing it to another a7750 movement I have it seems that the ratchet wheel driving wheel is the problems as shown in the red box in this diagram

 

 

 

I think he means this one...

Edited August 30, 2014 by 10:10 Watch Repair

[DR3M3L 4]

Whoops didn't see the OP

[nofitstate 27]

ETA gear sourced and pivot diameters ground down to 0.19mm to suit the A7750.

 

Thanks to this thread for giving me the inspiration to tackle this job http://www.rwg.bz/bo...?showtopic=1644

 

All of the movement is back together and amazingly it seems to be working!

 

I've just got to put the movement back in the case, which I'll do tomorrow evening. I really hope I don't have to take apart a 7750 movement again! That oscillating pin 60 seconds is a right pig!!!

 

Here's some photos I took while grinding the pinion diameter down.

 

 

 

 

 

 

[Cynikal.Mindset 1]

Or you could have just pressed the pinion out of the Asian 7750 gear and in to the Swiss gear.

[nofitstate 27]

Or you could have just pressed the pinion out of the Asian 7750 gear and in to the Swiss gear.

 

Not a solution in my case. It was pinion gear that had the stripped teeth.

 

 

[SSTEEL 0]

Well done mate

[10:10 Watch Repair 1]

Or you could have just pressed the pinion out of the Asian 7750 gear and in to the Swiss gear.

 

Not a solution in my case. It was pinion gear that had the stripped teeth.

Leaves.

[Sparky2 0]

So I've come across a problem on a7750 chronograph movement in that it doesn't self wind.

 

On close inspection of it and comparing it to another a7750 movement I have it seems that the ratchet wheel driving wheel is the problems as shown in the red box in this diagram

 

 

All of the auto winding gears seem to be functioning correctly and the teeth on the larger part of the ratchet wheel gear are all present, but it's not turning the larger silver gear with the 4 holes next to it. Anyway this leads me to believe that the smaller pinion gear that is part of the ratchet wheel must either be loose (I think they are pressed together) or broken.

 

Now I've done a small amount of work on watches since discovering reps. Such as dial and hand swaps, date wheel resetting and swaps, and I'm not to bad when using my hands, so I think I'm about ready to give this problem ago.

 

I've read a few online guides and discovered this very handy flash guide at disassembling a eta 7750 movement http://www.eta.ch/swisslab/7750/7750

 

So to anyone with experience with the a7750 movement is there any tricks or things that you think may come in handy to me?

 

Thanks!

 

Thanks for the great post! It has given me the courage to tackle my A7750 that does not autowind. I can still wind it by hand.

 

I have read 10 or 12 threads about this as well as watched as many videos that I could find. The issue with my 7750 is that the ratchet wheel driving wheel (32.033) turns, but the ratchet wheel does not. I can see that all of the outer teeth are fine, so I either have a loose ratchet wheel driving wheel pinion or the pinion has some bad teeth. In at least one of the threads that were discussing reducing the pinion’s diameter there was some talk that some thought that the newer A7750 movements with 28,800 vps had the same size pivot as the ETA 7750. These threads were old 2009 to 2011 and there was some disagreement about this.

 

So nofitstate, how old was your A7750. I see your post was recent. Have you heard anything definitive about this?

Edited January 17, 2015 by Sparky2

[nofitstate 27]

 

So nofitstate, how old was your A7750. I see your post was recent. Have you heard anything definitive about this?

 

My 7750 was only a couple of months old max when I started this thread. I can say with a lot of confidence that there are no A7750 movements that have the same ratchet wheel pinion size as the ETA7750, but I guess with Chinese movements you'll never really know what you are working with until you have a look.

 

As an update, since my fitting of the modded ETA gear (and the shortly later the removal of what looked like a curly pube wrapped around the balance spring pivot) my A7750 in my noob Breitling Superocean Abyss chronograph has been working perfectly

[Sparky2 0]

Thanks for the reply. I thought I had subscribed to this thread, but i guess not - no notification...

 

This is bad news for me. I cannot see me doing this mod. Perhaps if it were just polishing the pinion down to a smaller diameter I could handle it, but there is no way for me to tackle this with the lathe I have access to at work. It is even bigger than the one that you used and does not have a grinder.

 

I have not taken my movement apart yet, so I am not sure if it is the pinion gear’s teeth being bent or if the gear is just loose on the pinion. It seems to be not making good contact with the ratchet wheel anywhere during a 360 degree rotation, so maybe that means it is just loose. I hope so because I may be able to fix that. Otherwise I would need some help.

 

Would anyone want to turn a ratchet wheel driving wheel pinion down for me if I supplied it plus a few extra for their efforts?

[nofitstate 27]

Thanks for the reply. I thought I had subscribed to this thread, but i guess not - no notification...

 

This is bad news for me. I cannot see me doing this mod. Perhaps if it were just polishing the pinion down to a smaller diameter I could handle it, but there is no way for me to tackle this with the lathe I have access to at work. It is even bigger than the one that you used and does not have a grinder.

 

I have not taken my movement apart yet, so I am not sure if it is the pinion gear’s teeth being bent or if the gear is just loose on the pinion. It seems to be not making good contact with the ratchet wheel anywhere during a 360 degree rotation, so maybe that means it is just loose. I hope so because I may be able to fix that. Otherwise I would need some help.

 

Would anyone want to turn a ratchet wheel driving wheel pinion down for me if I supplied it plus a few extra for their efforts?

 

Best thing you can do is get it apart to see exactly what problem you have. If it the same problem as the one I had then I'm pretty sure a could help out.