Seiko 2628A – Technical Guide (High Quality)

The Seiko 2628A is a quartz analog movement developed in the early 1980s for ladies’ wristwatches, featuring three-hand timekeeping with a date complication. It belongs to the well-regarded 26xx family of compact quartz movements, known for reliability, accuracy, and ease of service. The 2628A was designed to deliver precise timekeeping in a small, slim format while providing convenient quickset date adjustment and hacking seconds for accurate setting.

1. Technical Specifications

2. Key Features

• Three-hand layout (hour, minute, central seconds)

• Date display at 3 o’clock

• Quickset date function via crown

• Hacking function allows precise time setting

• No day display, keeping layout clean and efficient

• Quartz-regulated timekeeping with excellent long-term accuracy

• Ultra-compact construction, ideal for slim ladies’ watches

• Low power consumption with two-year battery life

3. Calendar Operation

Setting the Time and Date:

• Crown Position 0 (pushed in): Normal operation

• Crown Position 1 (1st click):

  • Turn clockwise to quickset the date

• Crown Position 2 (fully pulled):

  • Turn to adjust the time

  • Second hand stops (hacks) to enable precise setting

⚠️ Do not use quickset between 9 PM and 2 AM, as the calendar gear is engaged and may be damaged.

4. Movement Design

Dial Side Components:

• Date wheel with jumper and driving finger

• Cannon pinion, hour wheel, and minute wheel

• Quickset gear and clutch spring

• Setting assembly: clutch, stem, and sliding pinion

Circuit Side:

• Quartz crystal oscillator (32,768 Hz)

• Integrated Circuit (IC) for pulse division and step motor control

• Step motor and rotor to drive the hand train

• Battery contacts, terminal insulators, and coil block

This configuration is compact, efficient, and designed for ease of battery replacement and calendar maintenance.

5. Battery and Power

Battery Replacement Instructions:

1. Open case back carefully using proper tools

2. Remove the old battery with plastic tweezers

3. Clean contact points if any corrosion is present

4. Insert new battery, ensuring proper polarity

5. Wait for the second hand to resume movement (within ~10 seconds)

6. Set the time and date; reseal the case with a new gasket if needed

⚠️ Always use ESD-safe tools to prevent static damage to the IC.

6. Troubleshooting and Solutions

7. Applications

The 2628A was widely used in ladies’ Seiko quartz watches from the early 1980s. These timepieces typically featured:

• Slim stainless steel or gold-tone cases

• Small round or oval dials with date window at 3 o'clock

• Simple baton or Roman numeral markers

• Acrylic or mineral crystals

• Elegant dress or casual styling

Common case references include:

• 2628-0030

• 2628-7000

• 2628-0010

8. Service Tips

• Avoid oiling plastic components

• Gently clean the date jumper and gear teeth with pegwood

• Always inspect coil block and step rotor for dust or debris

• Replace gaskets during battery change to preserve water resistance

• Use watchmaker’s blower or magnification to inspect calendar alignment

9. Conclusion

The Seiko 2628A combines Seiko’s quartz accuracy with essential practical functions like hacking seconds and quickset date, all within a small, robust, and low-maintenance package. It remains a dependable movement for vintage watch enthusiasts and repair specialists, continuing to serve in countless classic Seiko ladies’ models. With basic battery care and occasional service, the 2628A will keep ticking for decades more.