Valjoux 7750 terminal date change “feature”

Sometimes, it’s hard to understand what engineers were thinking when looking at some watch movement features. One of the worst offenders I can think oIMG_6499f is the otherwise excellent Valjoux 7750 chronograph movement.

Try to change the date with the quick-set function too close to midnight, and you are in for a surprise – a sizeable repair invoice from your watchmaker!

Have a look at this Valjoux 7750. Next to the “14” on the date disc, you can see the brass coloured date change wheel, and the little triangular bit that should advance the date has broken off. You can see the same wheel as the day change wheel on the left and above, with the triangular tip intact.

Firstly, I can’t understand making a movement with such a “feature”. Yes, the manual for the watch will tell you not to quick-set the date close to midnight, but who reads manuals, and who remembers? Secondly, after lots of your customers have broken their date change wheels, and after a fair amount of decades, you might want to improve the construction to prevent this from happening?

Nope, no chance. ETA now makes these movements, they have been around for decades, and they still haven’t fixed the problem.

Who could come to the rescue? The Chinese! Quite a while ago, I took apart a Chinese 7750 clone out of curiosity, and noticed an interesting difference…IMG_6503

Yes, it’s that simple. The post on the wheel transports the date change tip, and if the quick-set is operated, the tip can just turn away clockwise. A Chinese engineer had to come up with this. And well done to him or her!

I have a few of these in stock, and use them when I get a 7750 with a broken date change wheel.

So, dear ETA boys and girls, how about copying this excellent little construction from the Chinese, and make your customers a bit happier than they are now? And, whilst you are at it, how about supplying us independent watchmakers with parts? 😉


35 thoughts on “Valjoux 7750 terminal date change “feature”

  1. Above post expressing that the proper service of this movement prevents such malfunctions is in fact correct. There is actually a safeguard implemented to prevent breakage of the day and date wheels. If you look closely at the intermediate setting wheel you would notice that it’s in two pieces: the top wheel is set onto a tube coming from the bottom wheel. The top wheel is what interacts with the day/date corrector, and is to slip on this tube if day/date change is attempted at inappropriate times. ETA specifies that lubrication is to be applied in the gap between the tube and the wheel. If lubrication of this location is neglected at service, the two parts can bind and force the day/date disks to rotate and break the day/date wheels if they are engaged with their respective disks.

      • Is the finger portion on the date/day wheel spring loaded or otherwise encouraged to reset back to position to engage with the day/date disks after displacement?

          • No I was asking about the Chinese made day/date driving wheels. I was concerned that after the fingers are pushed out of the way they wouldn’t be ready to engage the day/date disks without being reset first. After a bit more thinking it became clear that it would be irrelevant as the finger would be held back by the teeth on the disks until the peg comes around and contacts the finger. However through my thinking, I uncovered the real problem. This solution works with the date just fine, but does nothing for the day change that sets backwards. It would force the finger against the peg on the wheel as opposed to the date change which pushes the finger away from the peg. After more research I found that some clone movements have a one piece setting wheel, and that this solution is just a bandaid to the real problem for date only watches, as including the day feature on these clone movements will invariably result in critical failure if day change is attempted at inappropriate times, as opposed to ETA, which should not result in breakage if serviced properly.

  2. I have two of my Tissot PRS-516 watches with the Valjoux movement have the condition where the day wheel doesn’t change until nine hours after midnight! I’ve taken the best care of them and also previously knew about this.

    So, I’m sure that if I call Tissot, they will want to service it and screw me over for the over hall of the movement correct?

    NEVER had problems like this with my Seiko day-dates.

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  5. Well done to the Chinese for implementing this, but please be aware that this system is not a Chinese invention. This safety feature is common in European high-grade watches and indeed clocks, and has been around for over a hundred years.

  6. I have a friend that just showed me his Breitling A13370 with a broken date setting. I’m pretty certain this is due to this “feature” as I believe the 13370 is really an ETA 7750. Before I make a recommendation, can someone point me to a source for the Chinese replacement component??


  7. Theres a friction on the rocker carrying the date advance wheel, so this doesnt have to happen if you advance the date near midnight, but it can. They should rectify it yes.

  8. ETA does not do the upgrade because they don’t have to.
    The part does not simply break because of the poor construction. If date change wheel pin breaks, it tells you the watch needs a service.
    Although the manufacturer advise not to change the date near midnight, a freshly serviced movement would allow you to do so without a problem.
    The original replacement part is cheap. The service is the problem. Some tend to service their watches when they only stop working.

      • Of course,. Even the humble Seiko 7S26 tolerates quick day and date changes at any time due to it flexible plastic fingers. Some people just speak like parrots without knowing any better.

  9. Oh yeah, I remember I the same happened to my ETA2892 based watch back in the days. Luckily it was repaired as warranty case, but it was both quite surprising and annoying as no manual supplied with the watch and how the hell I suppose to know about that..
    I am wondering if all those Omega (and other) movements based on 2892 also have the same design flaw?

  10. It is odd that ETA doesn’t bother to set this problem right. From what I know, the 7750 has been around since 1972, so that should have given them plenty of time. It looks as though they just don’t care….

      • Come to think about it, the Swiss version will market their date change wheel as a “you can switch back the date if you travel back in timezone” after midnight.

        For the Chinese to market this “feature”, they will need another pin to hold back the rotation when setting the time backwards pass midnight, but will need to move a lot more back.

  11. Forget ETA, let’s start looking to the Chinese to make cheaper replacement (and improved) parts for these old Swiss movement…

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