7750 date wheel doesn't change all the way

mattaus · Mar 1, 2019

Hi all,

I changed the date wheel on my beater 7750 and now the date doesn't fully change over - you can still see the top of the previous day's number and it's then stuck like this for every day there after - showing a little bit of the previous day. So basically after being set the first time, it doesn't quite fully switch to the next date after midnight and then is perpetually not quite right until manually set again (ti does change and it does rotate through enough degrees, but only after the first date change. Any change after that is sort of a degree short if that makes any sense?).

Also, I don't use this watch often so I can't recall, but there is no satisfying "click" when setting the date (as opposed to the day which does click as each day is passed over).

Anything straight forward to look in to that might be causing this issue? Or have I broken it in the act of changing the wheels over?

Thanks!

Archer · Mar 1, 2019

When was the last service?

duhgluss · Mar 1, 2019

Was the date wheel OEM or after market?

dirtvictim · Mar 1, 2019

Rule of thumb with day/date changing on any watch.
Always adjust the time forward until you see the D/D click over, this is how you know where midnite is approx.
Never adjust the D/D with the quickest while in the change over cycle which is typically 9pm-3am.
Once you know where midnite is you can advance the hands past midnite to the current time and proceed to adjust the D/D with the quickest just not between 9p-3a.
If this doesn't solve your problem then a service is likely necessary.

Vicc · Mar 1, 2019

Did you make sure you got a date wheel that corresponds with the date window?

mattaus · Mar 2, 2019

Thanks for all the replies guys. I'll have to send it in for a service - I've done everything by the book and all parts are appropriate. Not sure what I've done with this one!

Klaus Tickalot · Mar 3, 2019

Hi mattaus,
there are not many possible faults.
Remove dial, if the day changes correctly then datewheel is touching dial.
Else remove 2535 and check position of part 2569. Is the nose on left or right side of the smal spring of the calendar platform? (My hobbyist guess it is to the left. Then put it to the right side.)
Else check 2576 and 2611.

Assumed all is clean and lubricated correctly you'll find the fault.
Klaus

mattaus · Mar 3, 2019

Thanks Klaus. I'll have to open the movement up again tonight and look.

That said, I had it open yesterday and noticed that the mechanism for actually advancing the date wheel at midnight engages too early and disengages too early as a result, which causes the date to not be centred in the date window. I think it is part number 2556 in this picture: http://chronomaddox.com/valjoux/7750/eta_7750_page8.jpg (It's called the "Date indicator driving wheel" from my googling).

One problem - my driving wheel seems different from all the images I am finding. My wheel as a small nodule on the gear itself and the smaller wheel with the single tooth is free spinning. The larger gear (and hence the nodule) complete one full revolution every 24 hours. As the nodule approaches midnight it pushes the single toothed gear around, when engages the date wheel and advances it one "date". This is engaging too early and then disengaging too early as a result. So it's moving the date wheel the right distance, but it's just doing it at the wrong time/too early.

This makes me the think the driving wheel needs to be reset/realigned but I wouldn't even know where to start trying to do that! Alternatively the text on the date wheel might have been mis-printed, but then again the new and old date wheel are having the same problem plus the new wheel worked fine in the movement it came from, so it can't be that.

At least I know what it is called now so I can google some more

Vicc · Mar 3, 2019

mattaus said:
Thanks Klaus. I'll have to open the movement up again tonight and look.

That said, I had it open yesterday and noticed that the mechanism for actually advancing the date wheel at midnight engages too early and disengages too early as a result, which causes the date to not be centred in the date window. I think it is part number 2556 in this picture: http://chronomaddox.com/valjoux/7750/eta_7750_page8.jpg (It's called the "Date indicator driving wheel" from my googling).

One problem - my driving wheel seems different from all the images I am finding. My wheel as a small nodule on the gear itself and the smaller wheel with the single tooth is free spinning. The larger gear (and hence the nodule) complete one full revolution every 24 hours. As the nodule approaches midnight it pushes the single toothed gear around, when engages the date wheel and advances it one "date". This is engaging too early and then disengaging too early as a result. So it's moving the date wheel the right distance, but it's just doing it at the wrong time/too early.

This makes me the think the driving wheel needs to be reset/realigned but I wouldn't even know where to start trying to do that! Alternatively the text on the date wheel might have been mis-printed, but then again the new and old date wheel are having the same problem plus the new wheel worked fine in the movement it came from, so it can't be that.

At least I know what it is called now so I can google some more

That would only result in the date changing at the wrong time, it would still change all the way. If you wanted it to change at the right time you'd just have to realign the hands (unless its a day/date movement in which case you have to synchronize the calendars first)

mattaus · Mar 4, 2019

Thanks Vicc. I don't believe it is a hand alignment issue, the numbers on the date wheel are not lining up with the date window. Something is wrong - after watching a few videos since my last reply, I see that the date should "click" into place. Mine is not doing that and is almost waiting for the click/snap into place to occur. I've broken something! Bugger...

Vicc · Mar 4, 2019

mattaus said:
Thanks Vicc. I don't believe it is a hand alignment issue, the numbers on the date wheel are not lining up with the date window. Something is wrong - after watching a few videos since my last reply, I see that the date should "click" into place. Mine is not doing that and is almost waiting for the click/snap into place to occur. I've broken something! Bugger...

Like Klaus said the corrector (part #2569) might be also out of place which would be an obstacle for the date disk to clear. Either way you have to remove the dial to determine whats wrong. You could take a picture for us once you do and we may help you better.

bounder · Mar 4, 2019

Does this 'nodule' look the same as mine below? The date finger - they didn't bother with the day finger - has a sort of safety arrangement. It's driven in one direction by the pin in the wheel and free to spin in the other. Mine is a cheap no-name high beat clone I'm burning the midnight oil with right now, using to practise for the BHI chronograph bench test in May.

It's not bad but *not* a true copy so less than ideal to practise on. For instance, I've noticed the endstones are the same size in this clone, but looking up the Inca sheets the balance side should be much larger. This also makes it hard to decide how close the seating is to the real deal, I'm a bit worried about turning hollow pushers to match my clone, only to discover they won't fit in the exam (or worse, collapse it...)

If yours is like mine, the jumpers are quite a bit different to the tech sheet. My day jumper is adjustable, it pivots on an eccentric screw! Both the fingers should point to the stamped indicator on the clone's plate for the date to change just before the day. That's something I read on a forum, not my deduction - thanks to whoever posted that, if I find it again I'll link back.

mattaus · Mar 4, 2019

Holy hell. I actually fixed it. Turns out that the jumpers spring (2611) had jumped (pun intended) the date jumper (2576). This was causing the missing "click" I talked about earlier and was preventing the date from sitting perfectly centered in the date window.

I have never attempted anything like this before so to say I am pleased with myself is an understatement, even if I caused the problem in the first place lol. It's also highlighted the need for better lighting (I worked under my phone light only) and a better tool kit - the $10 eBay job I have worked, but this all might have been easier with some higher quality tools. My tweezers being magnetized certainly was a PITA and the lack of any magnifying devices made things tricky. I should invest in a loupe.

I'll also let you know the jumpers spring only went flying twice, and I spent no more than 1 hour looking for a screw I dropped. Everything is so bloody small...

Massive thank you to Klaus - that picture you provided and the advice to look at certain parts was invaluable!

mattaus · Mar 4, 2019

bounder said:
Does this 'nodule' look the same as mine below? The date finger - they didn't bother with the day finger - has a sort of safety arrangement. It's driven in one direction by the pin in the wheel and free to spin in the other. Mine is a cheap no-name high beat clone I'm burning the midnight oil with right now, using to practise for the BHI chronograph bench test in May.

It's not bad but *not* a true copy so less than ideal to practise on. For instance, I've noticed the endstones are the same size in this clone, but looking up the Inca sheets the balance side should be much larger. This also makes it hard to decide how close the seating is to the real deal, I'm a bit worried about turning hollow pushers to match my clone, only to discover they won't fit in the exam (or worse, collapse it...)

If yours is like mine, the jumpers are quite a bit different to the tech sheet. My day jumper is adjustable, it pivots on an eccentric screw! Both the fingers should point to the stamped indicator on the clone's plate for the date to change just before the day. That's something I read on a forum, not my deduction - thanks to whoever posted that, if I find it again I'll link back.

Sorry bounder! I only just saw your post now. So based on what you've written I too am working on a clone... This was a cheap garage sale find, non-branded watch. No skin off my back. I've learned a lot these last few days!

mattaus · Mar 4, 2019

*accidental double post*

7750 date wheel doesn't change all the way

mattaus

Archer

duhgluss

dirtvictim

Vicc

mattaus

Klaus Tickalot

mattaus

Vicc

mattaus

Vicc

bounder

mattaus

mattaus

mattaus

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