The Seiko A039A is a vintage quartz movement introduced in the early 1980s, representing Seiko’s commitment to creating slim, accurate, and affordable analog timepieces. Part of the A-series family, the A039A is a three-hand movement with a quickset day-date display. It was designed for thin case profiles and straightforward functionality, and it was commonly used in both dress and casual Seiko quartz watches during the 1980s.

Technical Specifications

• Caliber Number: A039A

• Movement Type: Quartz (step motor)

• Display: Analog – Hour, Minute, Center Seconds

• Calendar: Day and Date (quickset, bilingual on many models)

• Jewels: 0 jewels

• Battery Type: SR920SW (1.55V silver oxide)

• Battery Life: Approximately 3 years

• Accuracy: ±15 seconds per month

• Movement Dimensions:

  • Diameter: ~26.0 mm

  • Thickness: ~3.1 mm

• Hand Fitting Sizes:

  • Hour: 1.20 mm

  • Minute: 0.70 mm

  • Seconds: 0.20 mm

Key Features

The A039A was built for functionality and ease of daily use, with a reliable quartz oscillator and a practical calendar display. Its slim profile allowed it to be housed in thinner watches without sacrificing movement durability.

Main features include:

• Three-hand display (hour, minute, center seconds)

• Quickset day and date function

• Bilingual day wheel in many models (English + Spanish/French/Arabic, etc.)

• Non-hacking seconds – second hand continues running when setting time

• Day and date at 3 o’clock, with black or red print depending on the language or weekend indication

Crown Operation

• Position 0 (pushed in) – Normal operation

• Position 1 (first click) –

  • Rotate clockwise to set date

  • Rotate counter-clockwise to set day

• Position 2 (pulled out) – Time setting (second hand does not stop)

Do not use the quickset function between 9:00 PM and 4:00 AM, as this can damage the calendar gear train.

Battery Replacement and AC Reset

To replace the battery and reset the circuit:

1. Open the case back using the proper case knife or wrench.

2. Remove the used SR920SW battery with non-metallic tweezers.

3. Insert a new battery, checking polarity and contact integrity.

4. Locate the AC (All Clear) terminal, often labeled on the main plate.

5. Use metal tweezers to short the AC terminal with the battery’s negative terminal (case or contact spring) for 2–3 seconds.

6. Confirm normal operation resumes.

Resetting the circuit ensures the integrated circuit restarts properly after power interruption.

Maintenance and Service Tips

• Minimal lubrication is needed; most areas run dry by design.

• Clean calendar discs and setting gears to avoid jamming or misalignment.

• Coil block and step motor are sensitive components—handle with care.

• Replace the movement rather than attempting component-level repair if the IC or coil is damaged.

The A039A is well-suited to quick repairs and movement swaps due to its modular design and availability of donor watches.

Identification and Watch Models

The movement is marked “A039A” and is typically found in Seiko watches from the 1980s with reference numbers starting with A039, 7123, or 7N series. Watches featuring this caliber were usually stainless steel or gold-tone, with day-date windows and classic, understated dials.

Conclusion

The Seiko A039A is a practical and dependable quartz movement with day-date functionality, offering great value for collectors and wearers of vintage Seiko watches. With its slim size, long battery life, and simple maintenance needs, it remains a strong performer in the world of vintage quartz horology.