The Tissot caliber 6902 is a manual-winding chronograph movement from the 1970s, developed during the time when Tissot operated under the SSIH group alongside Omega and Lemania. Like its closely related calibers—such as 6912, 6922, and 6942—the 6902 is based on the reliable Lemania 1872 platform. Known for its simplicity, robustness, and ease of service, the 6902 offers excellent long-term performance when properly maintained.

Overview of the Caliber 6902

The Tissot 6902 features a bicompax chronograph layout, meaning:

• Central chronograph seconds hand

• 30-minute counter at 3 o’clock

• Running seconds at 9 o’clock

This layout, combined with a hand-wound mechanism, was typical for sporty and tool-style chronographs of the 1970s. The movement operates at 18,000 vibrations per hour (2.5 Hz) and is known for its cam-lever chronograph engagement system, which provides durability and is easier to maintain than column-wheel designs.

Watches equipped with this movement were often cased in stainless steel, with bold dial designs, tachymeter scales, and functional chronograph pushers.

Maintenance and Service Interval

For optimal performance, the Tissot 6902 should be serviced every 4 to 6 years. Even if the watch is running, internal oils degrade over time, and this can result in accelerated wear on gears, pivots, and chronograph components.

Signs that service is needed include:

• Chronograph hand stutters or skips

• Reset function fails to zero accurately

• Pushers feel stiff or stick during operation

• Irregular timekeeping or power reserve drop

• Audible grinding or friction when winding

Full Service Procedure

Servicing the 6902 should only be done by a professional watchmaker experienced in vintage chronograph movements. A proper overhaul includes:

1. Complete disassembly of the movement, including all chronograph components.

2. Ultrasonic cleaning of each part to remove aged lubricants and dirt.

3. Thorough inspection of key wear areas such as the clutch wheel, hammers, and heart cams.

4. Replacement of worn parts, including the mainspring and possibly clutch components.

5. Lubrication of specific contact points using high-quality watch oils.

6. Reassembly and chronograph adjustment to ensure proper engagement and reset.

7. Timing regulation in multiple positions for accuracy.

8. Case resealing, with new gaskets for the pushers, crown, and caseback if available.

Common Areas of Wear

With age and use, the following components may require attention:

• Reset hammers and heart cams – essential for the chronograph to reset precisely to zero

• Clutch wheel – wears with use and can slip if dry

• Pusher mechanisms – may lose spring tension or develop dirt buildup

• Mainspring barrel – weak springs can affect amplitude and reduce power reserve

• Balance and escapement – lubrication must be carefully reapplied for consistent beat rate

Best Practices for Daily Use

To preserve the movement and reduce wear:

• Always stop the chronograph before resetting it

• Wind the watch daily if worn, and stop winding when resistance is felt

• Avoid exposure to water and magnetic fields, especially if the case has not been recently resealed

• Store in a dry, stable environment to minimize condensation and corrosion risks

Conclusion

The Tissot caliber 6902 is a solid, proven mechanical chronograph movement that holds up well with proper care. Based on the Lemania 1872, it benefits from a modular, serviceable design and has good parts availability through vintage suppliers. Regular servicing and thoughtful handling will ensure the movement continues to operate accurately and reliably. For collectors and enthusiasts, the 6902 represents a dependable piece of Swiss chronograph history from a highly respected era in watchmaking.