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ETA 7751 triple full calendar; service, tips, tricks, watch-out fors, do's and don'ts advice please .....


Endeavor
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Hello All;

Got myself a nice little project; a triple full calendar 7751 with papers + box from first owner. The gold-plated watch (Berney-Bloneau S.A.) was purchased on 06 Nov. 1995, worn only on social events, never been serviced and never been opened ! (๐Ÿ™‚)

A do assume it's a standard grade 7750 (?)

7751-1.thumb.jpg.b742c5d1a6da0251747510ce24df63c5.jpg

(crown pulled out to prevent the watch from running)

7751-2.thumb.jpg.ff90fda7b5718121b532b679cf494060.jpg

On the timegrapher the movement runs with straight lines. Amplitude DD & DU around the 230 degrees and about 190 degrees in the vertical positions.

As far as I'm aware it's mostly a 7750 but before taking it apart, I like to fully understand the calendar works and perhaps its pitfalls; the do's and most importantly the don'ts.

- Any advice were to look-out for when disassembling the calendar works ? Any notorious "jumpers" underneath the calendar plate / disks?

The ETA Technical communication describes how to assemble the calendar driving wheel (position day-finger and month-finger) and some checks & adjustments.

- When assembling the calendar works are there any other points I've to be aware off ...... ??

My plan is to take pictures of the disassembly / assembly for a walk-through ......

Hope to hear ๐Ÿ˜‰

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Edited by Endeavor
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There's not too much to fret over if you've done a regular 7750 before. There are two wire click springs on the calendar plate that can jump, and 4 jumpers. Two use springs mounted on the plate, and two the wire springs shared with the moonphase advance lever and corrector. The jumpers for the date and year look identical, and they are, in spite of the manual showing different part numbers, so don't worry about mixing them up.

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If you've done a 7750 then you are already familiar with the spring for the hour counter hammer and zero lever, that one is always fun to put in place. There is a flat wire spring for the day corrector here, which is easy to overlook or think that it's secured in the plate, but it comes right out. The manual makes it clear how to orient it when reinstalling. The date advance wheel doesn't need to be oriented like the pair of wheels in a regular 7750 day-date, it advances everything in order without any fuss. Pay attention to the minute wheel- it has a little cap on the pinion which needs to go over the hour wheel teeth. This is easy to miss and will lock things up if not installed correctly. Normal 7750 doesn't have this.

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Otherwise just follow the (very good) manual for lubrication and assembly. They say not to service the barrel but of course you can and should if not replacing it. On a watch this old it might be a good idea to replace it along with the cannon pinion and reverser for the automatic and possibly the rotor bearing. Do the adjustments for the moonphase corrector (again well explained in the manual), the difference between locking up and not working at all is a very small adjustment.

Edited by nickelsilver
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Excellent, such an answer I was hoping for ๐Ÿ‘ Thanks a lot !!

Do you have any tips for removing the hammer-spring (45) without scratching the edge of Automatic device bridge (44)?

I know that there is a hole in it, but lifting the spring over the edge of the bridge and releasing the tension doesn't seem to, without making a small scratch, work very well for me. I also tried to carefully remove the bridge, holding the hammer down and then lift the spring ........ bit more tricky of having a "flyer".

What's your way of doing it?

BTW, can you see from the movement whether it's a standard grade?

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5 hours ago, Endeavor said:

Excellent, such an answer I was hoping for ๐Ÿ‘ Thanks a lot !!

Do you have any tips for removing the hammer-spring (45) without scratching the edge of Automatic device bridge (44)?

I know that there is a hole in it, but lifting the spring over the edge of the bridge and releasing the tension doesn't seem to, without making a small scratch, work very well for me. I also tried to carefully remove the bridge, holding the hammer down and then lift the spring ........ bit more tricky of having a "flyer".

What's your way of doing it?

BTW, can you see from the movement whether it's a standard grade?

You can put a piece of Scotch tape on the bridge, the translucent one, not the clear one (it sticks just enough but no residue), to protect from scratching with the hammer spring. I put both spring and hammer before the bridge; it almost always stays put (chrono in "run" mode so the hammer isn't on the chrono wheels). Iย  can only remember once in the last few years having one that didn't want to do that.

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Can't tell what grade it is. Even standard grade tends to hit chronometer level rates, or close to it, even after 30 years of being run without servicing. It's not the prettiest chrono but it's a runner.

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Thank you, I'll try the "running"-mode tape-method ๐Ÿ˜‰

Yes, it's amazing how accurate you get these 7750's to run when, if all else good, you spend time to adjust the Etachron properly.

I think I know enough to get started ๐Ÿ™‚

Thank you for your help so far ...... ๐Ÿ‘

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11 hours ago, nickelsilver said:

Master

Unlike some who like to think they are, you truly are ! ๐Ÿ˜‰ ๐Ÿ‘

The 7751 is back together, ticking & showing no less than the 11 functions very happily.

Awaiting new crystals to complete the case and for the final walk-through picture ....

Edited by Endeavor
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