7750 not working - gear train issue?

[vcelkamaja]

Hi, I’m new to this forum and hobby. Looking for some help from experts here:

- modified 7750 movement (6 and 12 subdials not used)

- not working with manual or automatic winding

- I removed the balance wheel and fully winded the movement

- then I gently move the fork up / down, up, down and everything works fine - escape wheel is moving. However if I continue, after ~20-30 cycles of manual moving of the fork the escape wheel doesn’t rotate anymore - I continue moving fork up and down but the escape wheel is not moving.

-then I wind the movement a bit more - or even just very gently rotate the crown - like 5 degrees or even less and then the escape wheel starts moving again when I continue moving fork up and down - again 20-30 fork cycles and the escape wheel stops moving again

- originally I thought the issue can be with the main spring but it is winded fine - if I “unlock” it it rotates very fast - has enough power reserve

- so my thinking is that it is probably something between the main spring and the es ape wheel - gear train?

- also I tried to remove the automatic winding - back side of the 7750 - rotating weight and the wheel but no change

 
any recommendation what can be wrong or what else I should check to localize the problem?  

[Klassiker]

It sounds like friction in the gear train. Let the power down in a controlled manner and remove the pallet fork. Wind a little power on. The escape wheel should spin and come smoothly to a stop, even reversing slightly at the end. If it doesn't spin, remove it and do the same test on the fourth wheel, and so on wheel by wheel back to the barrel.

Disassemble everything. Check for wear, damage and contamination, especially at the places where you found the most friction.

Reassemble, lubricate and repeat the test.

Never "unlock" with power in the system.

[vcelkamaja]

Thanks - so I tried to remove the fork and wind the movement slightly. What happens is that the escape wheel starts spinning but only for a short time. Actually when I do more winding it seems that the escape wheel is still moving only for a short time (independently on how much I wind). So I think the next step is to remove the escape wheel and check if the fourth wheel is moving. 

Unfortunatelly the escape wheel is positioned low so I would need to remove all upper decks (marked 1, 2, 3, 4 in attached photo) - which I'm afraid off...

 

[Nucejoe]

Loosen the screws to the upper deck and mainplate, see if that makes a difference. 

[vcelkamaja]

Wow, it seems it helped. I slightly loosen the screw on all 4 plates (see photo above) and the escape wheel runs well now. Also attached the fork and later also balance wheel and it is still running - great!

Unfortunately I can't say which screw helped. So I thightened all of them again now and the movement is running fine. 

Well... after 5 minutes it stopped moveing again  So I loosen all screws again and now it is not running...

Not sure if I should remove the balance wheel and fork again and try to repeat the same while keeping the screws a bit loosen...

 

 

[Nucejoe]

2 minutes ago, vcelkamaja said:

Wow, it seems it helped. I slightly loosen the screw on all 4 plates (see photo above) and the escape wheel runs well now. Also attached the fork and later also balance wheel and it is still running - great!

Unfortunately I can't say which screw helped. So I thightened all of them again now and the movement is running fine. 

Well... after 5 minutes it stopped moveing again  So I loosen all screws again and now it is not running...

Not sure if I should remove the balance wheel and fork again and try to repeat the same while keeping the screws a bit loosen...

 

 

 You released pretension forces in the plates, allowing space for any bent pivot, depthing ... etc to run . Usually pretension is due a bend in the plate caused by tightened screws. 

To find which screw/screws are causing this pretention.  Loosen all and tighten one at a time, then tighten and loosen one at a time. Once spotted shim the plate near or opposit side of the screws causing the fault, shim material must be real thin.

Lets ask @nickelsilver to correct me if wrong and his advice.

 

15 minutes ago, Nucejoe said:

 You released pretension forces in the plates, allowing space for any bent pivot, depthing ... etc to run . Usually pretension is due a bend in the plate caused by tightened screws. 

To find which screw/screws are causing this pretention.  Loosen all and tighten one at a time, then tighten and loosen one at a time. Once spotted shim the plate near or opposit side of the screws causing the fault, shim material must be real thin.

Lets ask @nickelsilver to correct me if wrong and his advice.

 

This all is true only if end shakes did exist when you reassembled.

 Shakes should be checked during disassembly/ reassembly.

Regds

[JohnR725]

14 hours ago, vcelkamaja said:

modified 7750 movement

modified by who? Who made this movement?

Then the problem you're having did it just suddenly happened or did you purchase it this way when did the problem pop-up?

[vcelkamaja]

3 hours ago, Nucejoe said:

 You released pretension forces in the plates, allowing space for any bent pivot, depthing ... etc to run . Usually pretension is due a bend in the plate caused by tightened screws. 

To find which screw/screws are causing this pretention.  Loosen all and tighten one at a time, then tighten and loosen one at a time. Once spotted shim the plate near or opposit side of the screws causing the fault, shim material must be real thin.

Lets ask @nickelsilver to correct me if wrong and his advice.

 

This all is true only if end shakes did exist when you reassembled.

 Shakes should be checked during disassembly/ reassembly.

Regds

what do you mean by end shakes please?

Maybe I should mention that I should use it without oscilating weight

2 hours ago, JohnR725 said:

modified by who? Who made this movement?

Then the problem you're having did it just suddenly happened or did you purchase it this way when did the problem pop-up?

I bought it knowing it is not working and trying to fix it. It is asian 7750.

[Nucejoe]

End shake is the axial free play of any arbour or balance staff 

Check end shake on all arbours of gear train including barrel that of the barrel.

Adjusting a jewel might be all your watch needs. 

Do you have a data sheet and diagram for 7750?  

 

 

6 hours ago, vcelkamaja said:

Not sure if I should remove the balance wheel and fork again and try to repeat the same while keeping the screws a bit loosen...

Wont hurt anything if you tighten the screws. 

 

[Klassiker]

9 hours ago, vcelkamaja said:

which I'm afraid off...

OK, that's understandable. If this watch is worth anything to you, my advice is to either take it to someone who knows what they are doing or put it aside until you have acquired the experience and confidence yourself.

[Nucejoe]

I agree with klassiker's advice.

Regds

 

[JohnR725]

5 hours ago, vcelkamaja said:

I bought it knowing it is not working and trying to fix it. It is asian 7750.

the problem with clones are how well were they cloned?

Then next problem of it's been modified was it ever running in the first place?

then there is the amusing problems? Amusing might not be quite right word but this is a chronograph it's complicated really complicated yet you seem to be missing the chronograph components? That's going to make it a lot simpler. But you still have amusing things?

5 hours ago, vcelkamaja said:

Maybe I should mention that I should use it without oscilating weight

for instance in not using the oscillating weight but if you look at the service mail but I  have down below that's not normally the way the oscillating weight is disassembled? Normally the screw what a come off and the ball bearing assembly would I go on with the weight so if it's just sitting there all by itself it makes you wonder how many other things have been not quite right?

 

 

ct_7750_esi_465853_16-1 13.08.2019.pdf

[vcelkamaja]

2 hours ago, Klassiker said:

OK, that's understandable. If this watch is worth anything to you, my advice is to either take it to someone who knows what they are doing or put it aside until you have acquired the experience and confidence yourself.

Thank you all for your comments and feedback. While I’m a complete beginner in this hobby I can accept the risk that I will damage this movement. I just wanted to give it a try to fix it. 
 

i tried to loosen and tighten all screws on the plates but no success. When I very gently wind (just a light touch) the winding in the ccw direction the escape wheel moves with me moving the fork up and down. But always only a few cycles.

I think I need to again remove the fork and investigate what happens to escape wheel to start moving again.

what should I imagine if you say “Adjusting a jewel”?
 

i think the issue is really in the gear train so I need to find where is it and what to do with it.

What is strange is that when I loosen the plate screws it started moving, so I assembled again the fork and balance wheel, tightened the screws and after 5 minutes it stopped. Loosening the screws didn’t help now so I thing removing the fork again is what I should do.

[Klassiker]

You will need to do a complete strip-down, clean, parts inspection, step-by-step rebuild and functional checks at each stage to diagnose the problem(s). Depending on what you find, you may or may not have the equipment or skills to correct the faults. If you are still curious enough to proceed despite the risks, there are plenty of people here who will assist you as far as we can. Just be aware, there is a good chance of you introducing new faults as well as not resolving the existing ones. On the other hand, faint heart never won fair lady!

 

 

[Neverenoughwatches]

42 minutes ago, Klassiker said:

You will need to do a complete strip-down, clean, parts inspection, step-by-step rebuild and functional checks at each stage to diagnose the problem(s). Depending on what you find, you may or may not have the equipment or skills to correct the faults. If you are still curious enough to proceed despite the risks, there are plenty of people here who will assist you as far as we can. Just be aware, there is a good chance of you introducing new faults as well as not resolving the existing ones. On the other hand, faint heart never won fair lady!

 

 

That's how I got my missus. Brave and bold got me  a  beauty 

[Nucejoe]

2 hours ago, vcelkamaja said:

.what should I imagine if you say “Adjusting a jewel”?

You move the jewel in or out in the hole its in, so to create some end shake needed for gears to turn effortlessly. 

 

Just now, Nucejoe said:

You move the jewel in or out in the hole its in, so to create some end shake needed for gears to turn effortlessly. 

 

It would be nice to show in a vid what you describe here,   A picture is worth two thousand words.

[Neverenoughwatches]

21 minutes ago, Nucejoe said:

You move the jewel in or out in the hole its in, so to create some end shake needed for gears to turn effortlessly. 

 

Hi nucejoe. I'm looking for a jeweling tool.  Would you recommend one with a hand lever as opposed to without for better depth control. Bit off topic but I thought I would grab an opportunity to ask you.

Edited April 28, 2022 by Neverenoughwatches

[Nucejoe]

3 hours ago, vcelkamaja said:

I think the issue is really in the gear train so I need to find where is it and what to do with it.

Yes,the issue is in the gear train and is very  likely an end shake one and we are trying to show you how to spot it.

[Jon]

1 hour ago, Nucejoe said:

Yes,the issue is in the gear train and is very  likely an end shake one and we are trying to show you how to spot it.

It's a pity we can't post a video. I've got a great one I show my students how to check end-shake, filmed under a microscope

21 minutes ago, Jon said:

It's a pity we can't post a video. I've got a great one I show my students how to check end-shake, filmed under a microscope

So, if when the screws are screwed tightly, you may have the jewel Shown in red in the pic) which the pivot passes through bind tightly against the shoulder of the pivot (which passes through the centre of the jewel shown in red) which doesn't allow for any up and down movement of the wheel, therefore the power can't flow properly, stopping the watch. Sometimes the jewel has moved and needs pushing out to regain that end-shake, which really requires a special tool. It could be either the jewel in the mainplate or the bridge, so either top or bottom jewels, so with tweezers you would hold the spoke of each wheel and see if it can move up and down slightly. you should feel it more than see it. more end-shake on the bigger wheels and less on the escape wheel and balance. 

I must say, I like your enthusiasm starting with a 7750, regardless of being a clone or not! He who dares, wins!

BTW, that was a slide from a lesson regarding oiling, just in case you thought what oil had to do with anything... lol

Edited April 28, 2022 by Jon

[utzelu]

On 4/28/2022 at 10:17 PM, vcelkamaja said:

Thank you all for your comments and feedback. While I’m a complete beginner in this hobby I can accept the risk that I will damage this movement. I just wanted to give it a try to fix it. 
 

i tried to loosen and tighten all screws on the plates but no success. When I very gently wind (just a light touch) the winding in the ccw direction the escape wheel moves with me moving the fork up and down. But always only a few cycles.

I think I need to again remove the fork and investigate what happens to escape wheel to start moving again.

what should I imagine if you say “Adjusting a jewel”?
 

i think the issue is really in the gear train so I need to find where is it and what to do with it.

What is strange is that when I loosen the plate screws it started moving, so I assembled again the fork and balance wheel, tightened the screws and after 5 minutes it stopped. Loosening the screws didn’t help now so I thing removing the fork again is what I should do.

While I have no advice for your issue, as I am a beginner hobbyist myself, I recommend you watch some of the videos on this YT channel: https://www.youtube.com/c/ChronoglideWatchmaking. There you will find a wealth of watchmaking knowledge from a professional, including all about end shake and how to adjust it.

[Nucejoe]

On 4/29/2022 at 2:51 AM, Neverenoughwatches said:

Hi nucejoe. I'm looking for a jeweling tool.  Would you recommend one with a hand lever as opposed to without for better depth control. Bit off topic but I thought I would grab an opportunity to ask you.

Apologies for my late response, just didn't notice your post.

 I hope we get a good advice from those who know.  

Regds

 

[vcelkamaja]

On 4/28/2022 at 11:24 PM, Klassiker said:

You will need to do a complete strip-down, clean, parts inspection, step-by-step rebuild and functional checks at each stage to diagnose the problem(s). Depending on what you find, you may or may not have the equipment or skills to correct the faults. If you are still curious enough to proceed despite the risks, there are plenty of people here who will assist you as far as we can. Just be aware, there is a good chance of you introducing new faults as well as not resolving the existing ones. On the other hand, faint heart never won fair lady!

 

 

Thanks for all support. I ended by "merging" 2 different 7750 movements into one. I took a new asian 7750 and removed some parts - date wheel, top plate,... and replaced them with parts from the non working 7750. It seems that everything is ok and works fine now.

The only "issue" I have that it seems that the 9 oclock running second pinion pin is shorter compared to the old one. Which is bad as my small second hand has a short tube to be attached to the pin of the new 7750 running second pinion at 9 oclock. Not sure if the tube of the second hand can be somehow extended... I'm also trying to get a new small second hand with longer tube.