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How accurate can you get with IWC IW3789-01 / IW378901

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I think the spec is 4 seconds a day. It is an IWC-modified ETA7750.

Currently, fresh from an IWC full service, I am seeing 7-8 secs a day.

The watch had been to another "trade" watchmaker previously (to unsuccessfully attempt to fix the 3 sec per minute intermittent fault which I posted here previously) and he got it within 1 second a day, so clearly this is possible. He said he was Omega authorised. And that was before IWC got it for their £500 service, prior to which they reported a list of faults e.g. wrong power delivery, wrong this and that, loose hands, you name it.


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Evidently they can be adjusted better, so why don't watchmakers do it?

Does it take longer to do?

My understanding is that these watches (ETA7750 etc) have several adjustments, for each of several orientations. But does it actually take longer?

I have read from IWC that their company policy is to never have an IWC watch run slowly so if they allow 7 secs it means they adjust for 3.5 fast, plus or minus 3.5 seconds. Yet I had this watch adjusted for zero, plus or minus about 1 second.


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18 hours ago, Peter-H said:

A data point: the 7-8 secs fast has come down to 4-5 secs. Is that normal?

Guys, You think in a complittely wrong direction...

Accuracy adjustment is a verry delicate matter. The poin is not how accurate is able to be adjusted a watch at all, but how accurate is able to be adjusted a watch, when his owner is wearing it. If the watch is on my hand, it will give different error, compared with when it is on You hand... That is why there are specifications for the movement - how accurate it should be after servicing. If the accuracy is within the limits of specification, then the Service can not be blamed... This specifications protect the Service from the client!  Actually, it is usually possible to adjust the accuracy to 0 sec/day, for the owners way of wearing, but it will change next seasot, with the change of temperature, evaporation or getting old of the oil and many other factors...

Also, after servicing, a watch should be used for a mounth, and then readjusted, because the accuracy will slowly change and then stabilize - exactly this is happening here...

Also, usually there is only one adjustment for all positions, and if position error is out of the specification, then should be replacet the whole balanse. The adjustment of balance is possible, but it is a kind of art, and most of the servise workers are not artists...

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  • 4 weeks later...

Just buy a quartz!  I quite like the fact that my 7750 collection vary slightly.  It adds character to the watch.  I've always adjusted to as near as poss, always erring on gaining slightly, as it is easier to just pull the crown to stop and zero, then push to start!  So long as they are within manufacturers tolerances, I'm happy.  Mechanical watches will always vary, face up/down, crown up/down etc.

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