The Seiko 7A28A is a groundbreaking quartz movement that holds a special place in horological history. Introduced in 1982, it was the world’s first analog quartz chronograph—a revolutionary development that merged the precision of quartz with the mechanical appeal of analog chronograph hands.

Engineered with extraordinary attention to detail, the 7A28A was a true marvel of the early quartz era. Unlike many quartz chronographs that use plastic parts and minimal jewels, the 7A28A movement was built like a mechanical watch—with 15 jewels, metal gear trains, and no plastic components. Its robust, serviceable design has made it a cult favorite among collectors and watchmakers alike.

Key Specifications

• Caliber: Seiko 7A28A

• Movement Type: Quartz (analog chronograph)

• Jewels: 15

• Battery: Seiko 943 (modern equivalent: SR927W)

• Accuracy: ±10 to 15 seconds per month

• Battery Life: Approximately 2–3 years

• Chronograph Capacity: 60 minutes

• Chronograph Resolution: 1/10 second

Features and Display

The 7A28A features a fully analog display with four subdials, operated entirely by quartz-controlled stepper motors. It has:

• Central hour and minute hands

• 60-second chronograph hand (center sweep)

• 1/10-second counter at 3 o’clock

• 60-minute totalizer at 9 o’clock

• Small seconds subdial at 6 o’clock

Uniquely, the 1/10-second subdial does not operate continuously. It only moves when the chronograph is stopped, jumping to the recorded fraction of a second—an energy-saving measure that preserves battery life.

The fourth pusher (at 10 o’clock) is used for independent chronograph hand zero-resetting, allowing fine-tuning after battery replacement or service.

Chronograph Operation

• Start: Press the upper right button (Button A)

• Stop: Press Button A again

• Reset: Press the lower right button (Button B)

After stopping the chronograph, the 1/10-second subdial jumps to the correct final position. If you hold the reset button, the chronograph hands return slowly. Tap it once for an instant snap-back.

The top left button (Button C) is used for hand alignment and calibration, which is especially useful after battery changes.

No Date or Alarm

The 7A28A intentionally does not include a date or alarm function. Seiko designed this caliber with a purist, instrument-like feel, focused entirely on chronograph functionality. It paved the way for later models like the 7A38 (which added day/date) and 7A48 (which introduced moonphase).

Construction and Engineering

The 7A28A is not a throwaway quartz movement—it was built to be serviced, not replaced. Key highlights include:

• Metal gears throughout

• No plastic parts

• Independent motors for each chronograph function

• 15 synthetic ruby jewels for reduced friction

• Separate coils for timekeeping and chronograph functions

These features give the 7A28A exceptional longevity and repairability, much like a mechanical movement.

Battery Replacement and Reset

Battery: SR927W (1.55V silver oxide)

To replace the battery:

1. Open the case back carefully using a case knife or proper opener.

2. Remove the old battery using non-metallic tweezers.

3. Insert a new battery.

4. Reset the IC if necessary by shorting the AC contact to the battery + terminal using metal tweezers.

5. Re-align chronograph hands using the 10 o'clock and 8 o'clock pushers if needed.

This ensures all hands are synchronized and operating correctly after battery installation.

Famous Models and Legacy

The Seiko 7A28A was featured in several iconic watches, including:

• Seiko 7A28-7000 worn by Roger Moore in A View to a Kill (James Bond)

• Military-issue chronographs (RAF Gen 1, South African Air Force, etc.)

• Racing and aviation-inspired designs with colored subdials and tachymeter bezels

Its heritage and performance have made it a collector’s favorite, often dubbed “the mechanical quartz.”

Final Thoughts

The Seiko 7A28A isn’t just a quartz movement—it’s a horological milestone. With its fully analog chronograph, mechanical-grade construction, and no-compromise engineering, it set the standard for all quartz chronographs that followed.

Even 40+ years later, watches powered by the 7A28A are still ticking, timing, and turning heads. For enthusiasts who want the reliability of quartz but the soul of a mechanical chronograph, the 7A28A remains an all-time classic.