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7750 headache

nicoyenny
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nicoyenny Member

nicoyenny

Posted
Posted

HI all!

I have this weird problem with a watch I built for a friend, he told me to build it using an Asian 7750. I didn't want to, but oh well, I went and bought the "latest" version of the A7750 hi-beat, etc..

I finish the watch (first I took the movement apart and did a cleaning/rebuild/oiling). Aside from the parts being "flimsy" it wasn't out of the ordinary ...

It looks GREAT on the timegrapher (0.0s, great amplitude, ~ +2 secs/day) , yes, I did set the lift angle to 49 deg.

BUT the watch actually runs incredibly fast, it is gaining about 1/2 hour every 10 hours (!) . I did demagnetize it just in case but it didn't help.

Am I missing something?

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jeffc83 WRT Addict

jeffc83

Posted
Posted (edited)

My guess would be that the hairspring is touching something or even sticking to itself.  Check to see if it is true and the spring action is clean.

Edited by jeffc83
matabog Super WRT Addict

matabog

Posted
Posted (edited)

check the wheels and pinions teeth number and their ratios. calcul

Edited by matabog
nicoyenny Member

nicoyenny

Posted
  • Author
Posted

WOW!

Thanks for all responses, yes, a disassembly is on the works, escapement is perfect, and as mata said, I suspect the canon pinion might be the culprit. I am 85% confident (yes, I quantify my confidence) that I installed an ETA canon pinion, and doing math I see that there is an extra tooth somewhere ... time to pull the microscope :pulling-hair-out:. Of course, it won't happen until Friday...I am xtra busy for the next two days ..

On hindsight I should have pushed my friend to spend a little more and let me get an ETA ... well, practice makes perfect ....

noirrac1j Distinguished Member

noirrac1j

Posted
Posted
43 minutes ago, jdm said:

Christian is a top notch watchmaker and one can only learn big time from his way of thinking and doing.

Thats a fantastic link, @jdm. I've read several overhaul "stories" from this guy. They're very useful as references because of the knowledge base, and the guy also takes excellent pictures. Great methodology.

JC

matabog Super WRT Addict

matabog

Posted
Posted (edited)

I'm not saying it's not the canon pinion, but I was  suspecting one wheel in the wheel train. If it were the canon pinion, then the error in timekeeping would be much bigger.

Edited by matabog
noirrac1j Distinguished Member

noirrac1j

Posted
Posted
27 minutes ago, matabog said:

I'm not saying it's not the canon pinion, but I was  suspecting one wheel in the wheel train. If it were the canon pinion, then the error in timekeeping would be much bigger.

This is correct...and when its the cannon pinion it would likely be losing time.

JC

nicoyenny Member

nicoyenny

Posted
  • Author
Posted

Thanks!

Yes, I will inspect every wheel in the train ... I used a few ETA parts on the build, so there are a few suspects ...

Will report back when I find the culprit. (perhaps the second wheel, that is the one in the wheel train that I replaced for an eta version (!))

nicoyenny Member

nicoyenny

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Nothing yet!

I will do the disassemble/reassemble tomorrow or Saturday ...WAY too busy with "regular" work (the one that pays the bills :( )until tomorrow
 

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