Help With Diagnosis On A 7750 Movement

[DJT2]

Hi guys, a friend asked me to have a look at a watch that keeps stopping. So before I start to strip, clean & service the movement. I thought I'd see if I could attempt a diagnosis before any work starts.

OK, so I've placed it on the timegraph & fully wound the movement, I've already noticed the mainspring is slipping very easily.

On the timegraph in while the movement is upside down its losing approx - 30s/d infact fluctuating between - 15s/d & - 39s/d

Here's where the fun begins. When I spin the watch right side up all hell breaks loose. after a few mins in this position the watch stops.

I know I will be disassembling to find the fault, but just as an exercise I thought it would be good to see if it's possible to diagnose a problem strictly from the timegraph.

I'm leaning towards a cracked jewel, however the movement looks very dry.

Any thoughts would be welcome.

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[GeorgeClarkson]

Magnetized hairspring, maybe? But your cracked jewel seems more probable... I leave it to the experts..

[DJT2]

Magnetized hairspring, maybe? But your cracked jewel seems more probable... I leave it to the experts..

Hi George, I did consider the magnetised hairspring. But, discounted that due to the beat readings being so much apart when turning the movement. I thought it would be just as bad either way up if it was magnetised. But I could be wrong with that thought.

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[oldhippy]

First of all it's an automatic watch so you can't fully wind the mainspring, the main spring is a slip mainspring so it is meant to slip in the barrel. You want know if the spring is damaged until you take it out of the barrel. You say all hell breaks loose when it's in a certain position. To me that indicates all manner of things. The first thing is take out the balance and have a good close look at the hairspring first it could just be a speck of dirt catching it . A full service would be better. I don't want to sound rude but making a silly mistake about the understanding of an auto and its mainspring, are you sure you will be able to undertake such a task. If you get stuck there's plenty of helpers here ready to chip in.

[DJT2]

First of all it's an automatic watch so you can't fully wind the mainspring, the main spring is a slip mainspring so it is meant to slip in the barrel. You want know if the spring is damaged until you take it out of the barrel. You say all hell breaks loose when it's in a certain position. To me that indicates all manner of things. The first thing is take out the balance and have a good close look at the hairspring first it could just be a speck of dirt catching it . A full service would be better. I don't want to sound rude but making a silly mistake about the understanding of an auto and its mainspring, are you sure you will be able to undertake such a task. If you get stuck there's plenty of helpers here ready to chip in.

Hi oldhippy, whilst It will be my very first 7750 under the knife so to speak. I'm confident I'll be upto the challenge. Yes I'm aware it's an automatic watch which uses a slip mainspring, my comment regarding this was the fact there seemed very little to no resistance when winding. Perhaps no braking grease in the barrel or the wrong lubricant?

I'm aware without being disassembled & fully inspected there really is no way to accurately pin point the problem. However, as you said there is alot of highly experienced helpful members here, who I thought maybe at some stage in life may have came across a similar scenario & could guide me towards a location to concentrate on. I would hope, once stripped, cleaned, lubricated & regulated everything will be fine. [emoji1]

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[Andyclient]

My knowledge and experience is very limited compared to many others here , but from the fact that it actually stops when face up I would be thinking towards the balance , the balance bridge end , maybe a dry/damaged pivot or jewel

[DJT2]

My knowledge and experience is very limited compared to many others here , but from the fact that it actually stops when face up I would be thinking towards the balance , the balance bridge end , maybe a dry/damaged pivot or jewel

Thanks Andy, with my limited knowledge that's what I was leaning towards.

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[steven]

It seems to have a broken balance staff. Check the end shake of the balance wheel. If it's shaking a lot then that's it.

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[DJT2]

Bit of an update. I've stripped the movement & completed a quick inspection.

After checking the balance wheel etc.. It seems in good order the only thing I have found during the inspection & I'm hoping it will be the culprit, was what looked like a ball of fluff on one of the pallet stones. Hopefully a thorough clean of the movement will sort this.

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[JohnR725]

Seeing as how you have the watch apart already you probably don't need the tech sheet but just in case you can find it at the first link. Then the second link is a really nice visual step-by-step guide for disassembly assembly adjustment for this movement.

 

Then a note regarding using timing machines for diagnostics of watches in poor condition. If the graphical display is producing nothing that looks like a running watch then all of the numbers are probably incorrect. To produce numeric results the timing machine needs to be able to pick up a the waveform correctly watches in poor condition have poor waveforms will produce incorrect results numerically. But the graphical display such as yours will tell you that you have watch that has a problem. For instance if you have a watch with extremely low amplitude sometimes a timing machine will pick up the middle of the waveform rather than the end show a much higher amplitude then it really has. Sometimes you can tell if the timing machines having problems as it takes a long time for the numbers to appear other times the numbers might not appear at all if it can't find a usable part of the waveform to trigger off of.

 

then regarding your timing machine it's currently set the 52° this watch is 49° for the lift angle.

https://secure.eta.ch/csp/DefaultDesktop.aspx

http://www.eta.ch/swisslab/7750/7750.html
 

[DJT2]

Seeing as how you have the watch apart already you probably don't need the tech sheet but just in case you can find it at the first link. Then the second link is a really nice visual step-by-step guide for disassembly assembly adjustment for this movement.

Then a note regarding using timing machines for diagnostics of watches in poor condition. If the graphical display is producing nothing that looks like a running watch then all of the numbers are probably incorrect. To produce numeric results the timing machine needs to be able to pick up a the waveform correctly watches in poor condition have poor waveforms will produce incorrect results numerically. But the graphical display such as yours will tell you that you have watch that has a problem. For instance if you have a watch with extremely low amplitude sometimes a timing machine will pick up the middle of the waveform rather than the end show a much higher amplitude then it really has. Sometimes you can tell if the timing machines having problems as it takes a long time for the numbers to appear other times the numbers might not appear at all if it can't find a usable part of the waveform to trigger off of.

then regarding your timing machine it's currently set the 52° this watch is 49° for the lift angle.

https://secure.eta.ch/csp/DefaultDesktop.aspx

http://www.eta.ch/swisslab/7750/7750.html

Hi John, Thanks for the links, really appreciate it & as it's my first 7750 I'm sure they will be invaluable.

Great info about the timing machine, having the lift angle set wrong.. How would it affect the results?

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[Geo]

First of all it's an automatic watch so you can't fully wind the mainspring, the main spring is a slip mainspring so it is meant to slip in the barrel.

You can fully wind the spring on this movement with the crown. When the spring starts to slip inside the barrel it is fully wound.

I assume what you meant was, you can't wind the spring until the crown stops rotating like a manual movement.

[Geo]

Have a read of this thread if you haven't already done so, there is no better!

http://www.watchrepairtalk.com/topic/2309-eta-7750-service-walkthrough-the-industry-standard-chronograph/?hl=%2Bvaljoux+%2B7750

[Men]

Did you check if the balance hairspring was nice flat? Looking at your timing machine it might tough "the little triangle" which closes the opening of the regulator pin (to prevent the hairspring jumping out).

[Geo]

Did you check if the balance hairspring was nice flat? Looking at your timing machine it might tough "the little triangle" which closes the opening of the regulator pin (to prevent the hairspring jumping out).

Well worth checking!

[DJT2]

Did you check if the balance hairspring was nice flat? Looking at your timing machine it might tough "the little triangle" which closes the opening of the regulator pin (to prevent the hairspring jumping out).

Thanks for taking the time to respond. Just had a look & everything looks fine. 

[DJT2]

Have a read of this thread if you haven't already done so, there is no better!

http://www.watchrepairtalk.com/topic/2309-eta-7750-service-walkthrough-the-industry-standard-chronograph/?hl=%2Bvaljoux+%2B7750

Thanks Geo, the work done by Lawson on that walk through just blows my mind. Very very helpful. 

[clockboy]

Agree with Geo that was a really good walkthrough & by following it you cannot go far wrong.

Don,t make the mistake I made by mixing up the day & date jumpers. I didn't realise my mistake until fully assembled when the date did not always line up correctly.

[DJT2]

Agree with Geo that was a really good walkthrough & by following it you cannot go far wrong.

Don,t make the mistake I made by mixing up the day & date jumpers. I didn't realise my mistake until fully assembled when the date did not always line up correctly.

Thanks, good tip. I have to say it's alot more advanced than the other movements I've attempted. But with the extremely help links you guys have posted & the helpful suggestions, I'm no longer dreading the reassembly.

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[Watchdog]

Clock Boy.... My instructor gave me a good way to remember the day n date jumper....

My "date is fat", but maybe some "day" she'll be skinny ...

In other words the fatter one goes to date wheel..

I've enjoyed this reading everyone's input...

[Geo]

Clock Boy.... My instructor gave me a My "date is fat", but maybe some "day" she'll be skinny

Brilliant! :D

[Watchdog]

I'm really curious how this will turn out..

The amplitude was low no matter dail up or dail down. Both too low. Should be around 270-300 without chrono on.

As for as the lift angle, it only effect the amplitude , not the rate.

My guess is it just needs a service.

Inspecting the parts after taking it apart would have clued in on worn parts.

The eratron pins may need to be adjusted..???

Gosh, this is very interesting.... Looking forward to the answer ....

[DJT2]

I'm really curious how this will turn out..

The amplitude was low no matter dail up or dail down. Both too low. Should be around 270-300 without chrono on.

As for as the lift angle, it only effect the amplitude , not the rate.

My guess is it just needs a service.

Inspecting the parts after taking it apart would have clued in on worn parts.

The eratron pins may need to be adjusted..???

Gosh, this is very interesting.... Looking forward to the answer ....

Hi buddy, hopefully you should get it. I'm having a look at it today,

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[Geo]

The eratron pins may need to be adjusted..???

Either that or the sproggle shaft is too tight! :D

[Men]

I assume you mean etachron? This is not an etachron balance. By the way adjusting the distance of the regulator pin (same effect as turning an etachron) will primary influence the positional and regulating behavior....