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Discussion Starter #1
I recently purchased a Victorinox Airboss Mach 6 that is in brand new condition, keeps good time, but has the Valjoux chrono second hand "stutter" I've read about before. I'm going to have it serviced (the chrono hour hand is also not quite zeroed right), but I'm wondering how big a repair this is, and how much it can be improved.

I had a look at the second hand sweep with a high speed camera at work, and it's pretty obvious why it looks so jerky when you slow it down. While it does tick at the correct rate, the spacing is completely off, in random sequences like one large tick, two tiny ticks, etc. It occasionally misses a tick completely. It's kind of interesting watching it tick along with the actual second hand, which is perfectly smooth.
 

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I recently purchased a Victorinox Airboss Mach 6 that is in brand new condition, keeps good time, but has the Valjoux chrono second hand "stutter" I've read about before. I'm going to have it serviced (the chrono hour hand is also not quite zeroed right), but I'm wondering how big a repair this is, and how much it can be improved.

I had a look at the second hand sweep with a high speed camera at work, and it's pretty obvious why it looks so jerky when you slow it down. While it does tick at the correct rate, the spacing is completely off, in random sequences like one large tick, two tiny ticks, etc. It occasionally misses a tick completely. It's kind of interesting watching it tick along with the actual second hand, which is perfectly smooth.
It probably is the result of gear lash. Im not sure if it can be adjusted. There might be something to provide friction on the gear to keep the lash tight that can be adjusted.
The 7750 on my Hamilton jumps a very small amount if you watch it closely. While the one in my maurice lacroix is perfectly smooth.
Again im not sure if it is an adjustment or the grade of movement used :think:
 

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I seem to recall reading there is a spring that can make it a lot worse if it comes loose. I have a Victorinox Alpnach automatic chrono that is much, much smoother. The Airboss dial is larger, which probably amplifies the stuttering, but it's quite noticeably worse even taking this into account. Also, the sweep is very smooth if I hold the watch vertical.
 

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First thing I would check would be to make sure the second hand isn't loose. Does orientation of the watch seem to affect where the second seems to slip? For instance, keeping the watch vertical with 12 up, is the second hand slipping going up between 6 through 12 or is it random around the dial?

-T
 

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Holding the watch with the 12 pointed up, it stutters like crazy between about 12 and 6, then is relatively smooth the rest of the way. If I turn it upside down (6 pointing up), it's smooth all the way around. If I lay it with the face pointing up, it stutters at random all over the sweep. I'm sure it would behave differently in other orientations. Not sure if there is a pattern that would help diagnose the problem, though.
 

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Discussion Starter #6
Like the good engineering geek I am, here's a video showing some stuttering, though this example isn't particularly bad. You can see it miss two ticks in the first 20 seconds of the video, and the spacing isn't very even, which is what makes it look jerky at normal speed. Each tick is 1/8s.

http://vimeo.com/7735729
 

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I seem to recall reading there is a spring that can make it a lot worse if it comes loose. I have a Victorinox Alpnach automatic chrono that is much, much smoother. The Airboss dial is larger, which probably amplifies the stuttering, but it's quite noticeably worse even taking this into account. Also, the sweep is very smooth if I hold the watch vertical.
First thing I would check would be to make sure the second hand isn't loose. Does orientation of the watch seem to affect where the second seems to slip? For instance, keeping the watch vertical with 12 up, is the second hand slipping going up between 6 through 12 or is it random around the dial?
 

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Holding the watch with the 12 pointed up, it stutters like crazy between about 12 and 6, then is relatively smooth the rest of the way. If I turn it upside down (6 pointing up), it's smooth all the way around. If I lay it with the face pointing up, it stutters at random all over the sweep. I'm sure it would behave differently in other orientations. Not sure if there is a pattern that would help diagnose the problem, though.
That is the result of a loose gear lash. As the second hand sweeps downward it falls because of gravity due to the loose spring not providing resistance. Then when the teeth make contact again the second hand moves until it falls again due to gravity. Which causes the stutter. There is no stutter the rest of the way because the gears are lifting the second hand against gravity providing a constant gear mesh.
It should not effect the accuracy. IMO it is just unsightly. If you are sending the watch in anyways for the hands to be moved have them take a look.
 

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Discussion Starter #9
Thanks. I think I must have read practically every thread ever posted on this subject here and on other watch forums, and it certainly seems like this is generally a fixable problem. I figured it was probably a loose spring, since it's worse in certain orientations. I realize it doesn't affect time-keeping, but it bugs me to see the chrono hand not moving smoothly, since one of the main appeals of an automatic to me is the mechanical workings.

I found what sounds like a good watch repair place in Toronto here. Local options are pretty sketchy, unfortunately. Other than jewelry stores and kiosks, this is the only place that actually specifically advertises itself as a watch repair shop. I've been by there a number of times, and they definitely seem more clock-oriented, but the owner claims they do lots of watch repair as well. I don't have any reviews to go on, and I'm nervous about handing over my watch after reading "watchbreaker" review threads here :-(
 

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I have never had to send a watch in for repair, or go to a local watchmaker yet. I would also be worried about handing my watch over to someone to open it up, there are a lot of little parts in there and it is a very expensive item! How old is the watch? Is there any warrantee left to send it back to Victorinox? The hand not being alined sounds like a warrantee issue to me. With this being said I guess its like dropping your car off at a mechanics you will only feel comfortable if you trust them. Many people here have long relationships with their watchmakers and trust them very much. I am not sure on policies if they mess up though. But the 7750 is a pretty common movement and I am sure most watchmakers see them a lot. I would not bring it to a jewlery store or kiosk, im not even sure if they would do the kind of work you want. They are good for changing batteries, even then I trust myself more. I would give the place that you posted locally a try, if the price is reasonable and they seem like good people. I have found (by talking to them) that people who do this work do it because they truly enjoy time pieces and are honest people.
Good luck
 

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Congrats on the purchase of the Airboss.....that's a nice watch. I've owned quite a few of the high end Swiss Army watches and they are fantastic quality.

I've owned at least 10 7750 based watches and 2 of them have had this issue. One was a Hamilton Khaki Chrono which I sold, but my current Sinn 903 seems to have this problem. I know my movement is stamped 7750, but the subdials are in the 3,6,9 position.

If you wouldn't mind letting me know the rough cost to fix the watch, I would appreciate it. I am going to be listing this one up for sale soon, and would like to have this issue sorted out so the new owner doesn't have to deal with it.

I've timed the chrono and it doesn't seem to affect the performance.....it's just not very aesthetically pleasing on a "expensive" watch.
 

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Discussion Starter #12
I haven't had a chance to deal with this yet, unfortunately. I'm still extremely wary of trying out the local repair place, and physically taking it to the place I found in Toronto would be quite a pain. I found Shane Ede's page here, and he seems quite good based on past comments here on WUS. Haven't had time to give him a call yet, though.

I absolutely love this watch, and I've been wearing it every day since I received it. My Alpnach is getting lonely! I'm really keen to have the choppy chrono second hand fixed, because I use the chrono a lot, and it's really bugging me.
 

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Hi, I'm new to this forum and came across this post having Googled "Valjoux 7750 stutter". Realise the post is over 5 years old but hopefully some of you are still subscribed!

I've just bought a Davosa Vigo Chronograph with a Valjoux 7750 movement. I immediately noticed the slight stutter when starting the chrono. I am loathe to send it back since it was from Amazon and it is now discontinued, so they will probably refund me. Davosa will have me send it to their service centre in Germany (I live in the UK). I have read about the need to break in new automatic movements and that things normally improve over that breaking-in period.

So, my question is: could the chrono secondhand "stutter" improve during the break-in period, or am I stuck with it until I get it serviced? I might add the stutter isn't too bad IMO, however, being the owner of two other autos (not with this movement) it's a little unsettling not seeing a beautifully smooth sweep.

Thanks!
 

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Congrats on the purchase of the Airboss.....that's a nice watch. I've owned quite a few of the high end Swiss Army watches and they are fantastic quality.

I've owned at least 10 7750 based watches and 2 of them have had this issue. One was a Hamilton Khaki Chrono which I sold, but my current Sinn 903 seems to have this problem. I know my movement is stamped 7750, but the subdials are in the 3,6,9 position.

If you wouldn't mind letting me know the rough cost to fix the watch, I would appreciate it. I am going to be listing this one up for sale soon, and would like to have this issue sorted out so the new owner doesn't have to deal with it.

I've timed the chrono and it doesn't seem to affect the performance.....it's just not very aesthetically pleasing on a "expensive" watch.
The 7750 Has some ...... idiosyncrasies, along with its strengths. Watches with refined chronograph movements will put you out of pocket $7 - $10 and up, at least with the Swiss and German companies. A 7750 replacement movement is around $700. An F. Piguet used in Blancpain's Fifty Fathoms and Vacheron's Overseas is around $5,000.
 
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Holding the watch with the 12 pointed up, it stutters like crazy between about 12 and 6, then is relatively smooth the rest of the way. If I turn it upside down (6 pointing up), it's smooth all the way around. If I lay it with the face pointing up, it stutters at random all over the sweep. I'm sure it would behave differently in other orientations. Not sure if there is a pattern that would help diagnose the problem, though.
10 years on, and I just picked up this exact same watch NIB. It exhibits identical behavior, including being smooth when upside down with 6 pointing up, stuttering when dial up or 12 up. I know this is not an elabore grade 7753, but it seems like it might to be fixable.

Did you (or anyone else) ever get this resolved? This is the second one of these I got from the dealer that does this and I'm debating if I should keep it or give up and move on.
 

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10 years on, and I just picked up this exact same watch NIB. It exhibits identical behavior, including being smooth when upside down with 6 pointing up, stuttering when dial up or 12 up. I know this is not an elabore grade 7753, but it seems like it might to be fixable.

Did you (or anyone else) ever get this resolved? This is the second one of these I got from the dealer that does this and I'm debating if I should keep it or give up and move on.
There is a part called rocking pinion that engages with the chrono wheel when you start the chrono, that part could be adjusted with a screw how tight or loose the engagement to be, which in turn affects how smooth the chrono wheel turns, and it's a fine adjustment to get it perfect, so it's normal to see your watches behave like they do currently.
 

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10 years on, and I just picked up this exact same watch NIB. It exhibits identical behavior, including being smooth when upside down with 6 pointing up, stuttering when dial up or 12 up. I know this is not an elabore grade 7753, but it seems like it might to be fixable.

Did you (or anyone else) ever get this resolved? This is the second one of these I got from the dealer that does this and I'm debating if I should keep it or give up and move on.
There are two common items that need to be looked at - the engagement between the teeth of the oscillating pinion and the chronograph wheel, and the amount of friction the friction spring applies to the chronograph wheel.

Generally speaking the hand stutter is caused by not controlling the play in the gears. The driven wheel can actually get "thrown forward" of the gear that is driving it, and this causes a pause for the driving gear to catch up. The solution to this is installing a friction spring that puts a small amount of resistance on the driven gear, preventing it from coming out of contact with the teeth of the driving gear. This is not a problem that is limited to the 7750, and it can happen with any horizontally coupled chronograph, and also on vintage watches that are not chronographs, that have indirectly driven sweep seconds hands.

This video shows an Omega Speedmaster Pro, and in the first clip shows the watch with the friction spring installed, and the travel of the driven wheel on the left (the chronograph wheel that the large chronograph seconds recording hand is attached to) running smoothly. The second clip I've removed the friction spring completely to show how the driven wheel gets thrown ahead of the drive wheel, and stops while the drive wheel catches up:


Of course the stuttering here is greatly exaggerated, and it's very rare to see a watch run as badly as this is shown.

Although the stuttering isn't normal behavior for the watch, it's a fairly common fault that any competent watchmaker should be able to correct for you. If the watch is still under warranty, you can take it back and get them to fix it if you like. If it doesn't bother you then you can always wait for the first service.

Cheers, Al
 

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Is there - should there be a distinction regarding this issue? I've seen the "stuttering" issue where the chronograph hand doesn't sweep "evenly" through the clock range and appears to skip sometimes. I've also got a watch that I wouldn't say "stutters", I'd say the chronograph hand has a "pronounced" ticking - i.e. you can see the four beats per second movement vs being smooth, but it's very consistent and keeps accurate time/chronograph measurement. I can see it "smooth out" in the last second (59th second) which I assume has something to do with the gear train moving/clicking the minute counter over. AD says that this is within spec - and again, it times perfectly.
 

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There are two common items that need to be looked at - the engagement between the teeth of the oscillating pinion and the chronograph wheel, and the amount of friction the friction spring applies to the chronograph wheel.

Generally speaking the hand stutter is caused by not controlling the play in the gears. The driven wheel can actually get "thrown forward" of the gear that is driving it, and this causes a pause for the driving gear to catch up. The solution to this is installing a friction spring that puts a small amount of resistance on the driven gear, preventing it from coming out of contact with the teeth of the driving gear. This is not a problem that is limited to the 7750, and it can happen with any horizontally coupled chronograph, and also on vintage watches that are not chronographs, that have indirectly driven sweep seconds hands.

This video shows an Omega Speedmaster Pro, and in the first clip shows the watch with the friction spring installed, and the travel of the driven wheel on the left (the chronograph wheel that the large chronograph seconds recording hand is attached to) running smoothly. The second clip I've removed the friction spring completely to show how the driven wheel gets thrown ahead of the drive wheel, and stops while the drive wheel catches up:


Of course the stuttering here is greatly exaggerated, and it's very rare to see a watch run as badly as this is shown.

Although the stuttering isn't normal behavior for the watch, it's a fairly common fault that any competent watchmaker should be able to correct for you. If the watch is still under warranty, you can take it back and get them to fix it if you like. If it doesn't bother you then you can always wait for the first service.

Cheers, Al
Thank you, Al. This is a great video. Do you have any photos and/or videos of that spring itself? Looking at the ETA Swisslab site, it shows 65.160 as the clutch spring. Is this what you are referring to?

7750 clutch spring.png

The stuttering is much more pronounced when the mainspring is fully wound, which would potentially explain the chrono wheel being thrown forward as you explained.

It looks like the screw is actually accessible without removing the chrono bridge if the oscillating weight is removed, and the point where the oscillating pinion engages with the chrono wheel is visible through a small hole. Based on these observations, is it possible to make a minor adjustment without pulling the entire movement out of the case?
 

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Thank you, Al. This is a great video. Do you have any photos and/or videos of that spring itself? Looking at the ETA Swisslab site, it shows 65.160 as the clutch spring. Is this what you are referring to?

View attachment 14347107

The stuttering is much more pronounced when the mainspring is fully wound, which would potentially explain the chrono wheel being thrown forward as you explained.

It looks like the screw is actually accessible without removing the chrono bridge if the oscillating weight is removed, and the point where the oscillating pinion engages with the chrono wheel is visible through a small hole. Based on these observations, is it possible to make a minor adjustment without pulling the entire movement out of the case?
No that's not the spring - the part is this one the "chronograph wheel friction":



It goes under the chronograph wheel, so would require removal of the chronograph hand at least (so you can pull the chronograph wheel out), and disassembly of the chronograph bridge and parts under it. Here is the part in situ:



If you are adjusting the depth of engagement, the teeth of the oscillating pinion should engage with the teeth of the chronograph wheel to 2/3 of the tooth depth. This is slightly more than what would be the norm on other horizontally coupled chronographs, like the Speedmaster Pro uses.

Cheers, Al
 
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