Service: Breitling Chronomat B13050.1 / ETA 7750

IMG_9174Another day, another chronograph 😉 After the Kelek, it’s time for something more mainstream, a Breitling Chronomat. When it comes to the movement, the ETA (Valjoux) 7750, it doesn’t get more mainstream than that. This is the movement that is the most used in chronographs, and the one copied in China and ticking happily in all the fakes out there. And there is a good reason for that – it’s a good workhorse, beating at 28,800 bph.IMG_9176

Dear oh dear – it’s high time for a service!


First look at the ETA7750.IMG_9181

Before I remove the movement from the case, I take the rotor off.IMG_9183

With the movement out, the dial and hands come off next.IMG_9184

The bottom plate with date ring. The provision for a day ring is there as well, as you can have the 7750 as a day/date as well.IMG_9185

I start off with the top plate.IMG_9187

The chronograph layer becomes visible. The auto winder on the 7750 only works in one direction, and the little ratchet wheel (brass colour) is visible. Once thing I don’t like about the 7750 is the click spring for the auto winder ratchet wheel (and the one for the click wheel on the barrel). They are super-cheap wire springs fixed on to the plate. But that’s just an aesthetic consideration.IMG_9193

Most of the chronograph bits are gone, and you can see the barrel wheel.IMG_9201

The chronograph plate.IMG_9202

The gear train.IMG_9205

The old mainspring. As new ones are readily available, I will of course replace it.IMG_9207

Time for the bottom plate.IMG_9211

Below the date wheel, another plate sits on top of some other chronograph gears and the keyless works.IMG_9212

And here they are.IMG_9213

Almost cleared.IMG_9217

And ready for the cleaning machine.IMG_9225

The clean parts ready for reassembly.IMG_9226

Escape wheel, pallet fork and cap jewels after the epilame treatment.IMG_9257

With the new mainspring on the right, it’s time to get stuck in!IMG_9258

I start off with the mainspring.IMG_9260

Then the balance jewels go back in.IMG_9261

The gear train in place.IMG_9262

And the wheel bridge / chronograph bridge back in place.IMG_9263

I will put together the basic movement first, to make sure everything is working as it should, before reassembling the rest.IMG_9265

Here we are, ticking again.IMG_9266

Oh yes, that looks so much better!IMG_9267

In this photo, you can see the click spring blocking the click wheel. Worthy of a £5 Chinese movement, but a construction like this shouldn’t feature in a Swiss movement of this price range. It works, but it’s ugly.IMG_9270

All chronograph bits back in place.IMG_9271

Nice and clean.IMG_9273

Now I turn the movement over, and start on the bottom plate. The hammer for the hour totalizer is a blighter to put in – check out the assembly at the top at 12 o’clock – how the wire spring has to go over two parts. Very very tricky to put in without it flying all over the workshop.IMG_9274

All is safe under the plate now.IMG_9275

And the date wheel is back in place.IMG_9277

The dial and hands go back on.IMG_9278

And I can case the movement again.IMG_9279



Charles from WatchGlassCutting polished the case for me, and he did a great job.IMG_9510

Back in the case, with a new gasket.IMG_9513

Case back on.IMG_9515

Time for the waterproof testing – pass at the first try.IMG_9517And we are back in business!


11 thoughts on “Service: Breitling Chronomat B13050.1 / ETA 7750

  1. Christian, how much “better” technically would you say the basic El Primero cal. 400 is, compared to the 7750? Maybe it’s an unfair comparison since an El Primero is generally more expensive, but I’d love to hear your opinion.

    Love this blog btw. It’s like christmas everytime a new post shows up!

    • I’d say the two are worlds apart. Have a look at the El Primero –
      Everything there is made to be “best of breed”, and that’s the joy of the El Primero movement. There are no short cuts, and everything is properly thought through. From the high-speed base movement to every detail of the chronograph, the people that constructed the El Primero did their best. No wonder Rolex adapted the movement for their first Daytonas! In my book, one of the best chronograph movements there is.
      The 7750 is the Vauxhall Astra, the El Primero is the Porsche.
      But, let’s not forget that a Vauxhall Astra is a reliable and good car, just not as exciting. The shortcuts that were taken when the 7750 was constructed work, but some of them are a bit ugly. That click spring really grates me every time a service a 7750…

      • Thanks! That was kind of the answer I was fishing for, since I’m a sucker for chronos and recently treated myself to an El Primero after a string of 7750-based watches 😉

      • Hi all,

        I’m new to the site, but I’d like to add my humble opinon. Firstly whilst the el primero may have been a cutting edge design due to it’s high beat rate in 1969, today it’s old school lateral clutch is looking decidedly old tech next to the vertical clutch movements from Rolex, Piguet and Seiko’s spring drive 9r series. Maybe zenith should try designing something new rather than trading on such an old movement. Great work though!

  2. So that’s what my watch looks like inside… Shocked to hear its full of cheap bits!
    Nice job btw Christian 🙂

  3. I didn’t know the 7750 rotor only wound in one direction… presumably a space / component saving idea?

    A very smart looking watch.. if a bit chunky 😉

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.