ETA · Valjoux 7750

Sinn 103, IWC Pilot's Chronograph and Breitling power reserve: inside the Valjoux 7750

The Sinn 103, IWC Pilot's Watch Chronograph, classic Breitling Chronomat and many TAG Heuer Carreras run on the Valjoux 7750 or a close derivative. From full it runs for about 42 hours, or just under two days.

Updated September 2026 · Based on manufacturer specs, published reviews and watchmaker/owner reports

Watches that use the Valjoux 7750

The 7750 is the most widely used automatic chronograph ever made, so the list below is only a sample. Many brands rename it: IWC calls its modified version the 79320, Omega used it as the 1164, and TAG Heuer's Calibre 16 is a 7750 (or its Sellita SW500 clone) under another name. If your chronograph has a 30-minute counter at 12, a 12-hour counter at 6 and running seconds at 9, it's very likely a 7750.

Specs at a glance

History and where it came from

In 1969, Seiko, Zenith and the Heuer–Breitling group all launched automatic chronographs. Valjoux, the Vallée de Joux chronograph specialist, gave engineer Edmond Capt the job of designing one that was cheaper to mass-produce than the column-wheel designs of its rivals. His 7750 was built from the hand-wound Valjoux 7733. It swapped the column wheel for a cam and levers and wound in one direction only.

It launched in 1973–74, straight into the quartz crisis. Production stopped around 1975, and management ordered the tooling destroyed. Capt kept tools and drawings instead, and when mechanical chronographs came back in the early 1980s, the 7750 was ready. Breitling's 1984 Chronomat was one of the watches that brought it back.

It then became the default Swiss chronograph. IWC, Breitling, Omega, Tudor, TAG Heuer, Sinn, Hamilton, Tissot and hundreds of other brands have used it or built on it. Monochrome counts a long list of variants, from the 7753 with its 3-6-9 layout to GMT, moonphase and hand-wound versions. When ETA restricted supply to outside brands after 2002, Sellita launched a copy, the SW500. Swatch Group has since modernized the family itself: the A05.H31 in the Tissot PRX Chronograph and Hamilton's H-21 both stretch it to 60 hours.

Accuracy in the real world

Like the ETA 2824-2, the 7750 comes in grades from Standard up to chronometer, and the grade decides the factory tolerance. Brands also add their own work: aBlogtoWatch notes that IWC modifies and checks parts such as the hairspring for its 79320. It regulates easily at 4 Hz, and healthy examples commonly run within a few seconds a day once adjusted.

Running the chronograph draws extra power and lowers the balance amplitude slightly. That's normal. Leaving the chronograph running all day as a sweep-seconds hand isn't a good idea: it uses up the reserve faster and adds wear.

Reliability and servicing

Watchmakers call it a tractor. It's thick and not especially elegant, but it's robust, and almost every watchmaker has serviced one. Monochrome's long look at the movement found that most reported problems came from mishandling rather than design faults.

• Service cost. A chronograph service costs more than a time-only one because there are more parts to clean and adjust. The 7750 is still one of the cheapest chronographs to maintain, because parts and know-how are everywhere.
• Checking a used one. Run the chronograph for a few minutes, then reset it. All three hands should snap back to zero every time. Hands that creep back or stop short point to worn hammers or heart cams.
• Scraping rotor. A smooth whirr is normal. A gritty scraping means a worn rotor bearing and needs a service.

Quirks worth knowing

• The wobble. The rotor only winds in one direction and spins freely in the other. On the wrist you feel it swing and hear it whirr. It's the design, not a fault.
• Stiff pushers. A cam chronograph needs a firmer press than a column wheel. Reviewers often describe it as stiff; it's less crisp, but tough.
• Date danger zone. Don't quickset the day or date late in the evening or early morning, when the calendar gears are engaged. Monochrome gives 8pm to 2am; we suggest avoiding roughly 8pm to 3am to be safe. It's the most common self-inflicted 7750 repair. Here's how to set it safely.
• Thickness. At 7.9 mm before the dial and hands, 7750 watches are chunky. The Sinn 103 and IWC Pilot's Chronograph both wear tall for that reason.

How it compares

• Sellita SW500: a close copy for brands outside Swatch Group, with the same character and quirks.
• ETA A05.H31: the modernized 7753 in the Tissot PRX Chronograph, with 60 hours of reserve.
• Hamilton H-21: an updated 7750 with a 60-hour reserve, the easiest upgrade within the family.
• Zenith El Primero 400: an integrated column-wheel design running at 5 Hz. More refined, and much more expensive to buy and service.
• Omega 3861: the hand-wound, column-wheel Speedmaster Moonwatch calibre. Thinner and more traditional, but you wind it every day.

Living with the 42-hour reserve

Depending on the version, a 7750 runs for about 42 to 48 hours from full. We list 42 hours, the conservative figure aBlogtoWatch gives for the Sinn 103. That covers a night off the wrist but not a weekend: take your Sinn 103 or IWC Pilot's Chronograph off at 6pm on Friday and it will have stopped by Sunday lunchtime. Run the chronograph on Saturday and it stops sooner.

A stopped 7750 costs more effort than a three-hander. You reset the time, the day and the date, and you have to avoid the late-evening danger zone while doing it. That's why owners with a rotation plan ahead. Watch Winder counts down the reserve for each watch and reminds you before the chronograph stops, so you can wear it or give it a few turns of the crown first. To check a specific weekend, use the "Will my watch stop?" calculator.

Verdict

The Valjoux 7750 isn't pretty, subtle or thin. It is the movement that kept the Swiss mechanical chronograph alive, and it's why a Sinn 103 or an IWC Pilot's Chronograph is as easy to service as it is to wear. It's tough, accurate once regulated, and serviceable almost anywhere. The weak spot today is the short reserve. Accept the wobble, respect the date window, keep it wound, and it will last for decades.

FAQ

How long does a Sinn 103 run off the wrist?

About 42 hours from full, which is just under two days. Running the chronograph shortens that.

What is the power reserve of the IWC Pilot's Watch Chronograph?

About two days. IWC's calibre 79320 is a modified Valjoux 7750, commonly listed at 44 hours, so it won't survive a full weekend off the wrist.

Why does my Breitling Chronomat wobble on the wrist?

If it has a 7750-based movement, the rotor only winds in one direction and spins freely in the other, so you feel and hear it swing. That's normal; only scraping or grinding means a problem.

Is the TAG Heuer Carrera Calibre 16 a Valjoux 7750?

Yes. Calibre 16 is TAG Heuer's name for a 7750 or its Sellita SW500 clone, with the same layout, reserve and behavior.

When is it safe to change the date on a 7750?

Outside the late evening and early morning, roughly 8pm to 3am. Advance the hands until the date flips (that's midnight), move them on to mid-morning, then use the quickset.

Is the Sellita SW500 the same as the Valjoux 7750?

It's a close copy with the same layout and behavior, made by Sellita for brands that can't buy ETA movements.

Can I leave the chronograph running all the time?

It won't break it, but it uses more power, shortens the reserve and adds wear. Most watchmakers advise against it.

Sources

• Monochrome: Everything you should know about the Valjoux 7750
• Teddy Baldassarre: Valjoux 7750, the story of the world's most famous chronograph
• Gear Patrol: The iconic Valjoux 7750 chronograph movement
• aBlogtoWatch: Sinn 103 St Sa E hands-on
• aBlogtoWatch: IWC Pilot's Watch Chronograph 3777 hands-on

Keeping it running

• On an average day an automatic gains roughly 4 hours of reserve per hour on the wrist, so about 10 hours of wear fills the Valjoux 7750. Desk days charge more slowly.
• Most automatics can also be wound by the crown. If yours has stopped, a few dozen turns gets it going before you put it on.
• Off the wrist it stops about 42 hours after it was last full. Stopped sooner?
• On a watch winder, start at about 800 turns per day, clockwise. Winder settings for every movement.
• If it does stop, don't set the date between 9pm and 3am. Check if it's safe.

All ETA movements

Never let it stop

Watch Winder counts down the reserve of every watch you own and reminds you before one stops. It already knows the Valjoux 7750: type your watch's name and the reserve fills itself in.

Manufacturer's published figure. Real reserve varies with the watch's age and service; check your manual.