The Seiko A628A is a unique and advanced quartz digital LCD movement introduced in the early 1980s, best known for powering Seiko's innovative "TV-style" digital watches. This caliber is part of Seiko’s creative approach to digital timekeeping, combining a dot matrix LCD with multiple functions, such as time, date, alarm, and a distinctive text display format. It stood out in the market with its horizontal screen layout, mimicking the look of a television screen—hence the nickname “TV watch.”

Technical Specifications

• Caliber Number: A628A

• Movement Type: Quartz (Digital LCD)

• Display Type: Dot-matrix Liquid Crystal Display (horizontal rectangular screen)

• Primary Functions:

  • Timekeeping (12-hour format)

  • Calendar (Day and Date)

  • Daily Alarm

  • Hourly Chime (on/off)

• Backlight: Not integrated in the module (some models featured external case lighting)

• Battery Type: SR1120W (1.55V silver oxide)

• Battery Life: Approx. 2 years

• Accuracy: ±15 seconds per month

• Module Dimensions:

  • Width: ~26 mm

  • Height: ~22 mm

  • Thickness: ~5 mm

Display Layout

The Seiko A628A is known for its distinctive landscape LCD with a dot-matrix segment display, which allowed more stylized numerals and symbolic representations.

• Top line: Displays day of the week and AM/PM indicators

• Main display area:

  • Time shown in HH:MM format

  • Seconds often displayed separately or animated

  • Some models scroll or blink during setting modes

  • Alarm and chime indicators displayed as small icons

This layout creates a "mini screen" feel, reminiscent of early computer or television monitors.

Operating Modes

The A628A is relatively minimalistic in function but elegant in execution. The watch cycles through several core modes using the primary mode button:

1. Time Mode

• Displays the current time in hours and minutes

• 12-hour format only, with AM/PM displayed

• Animated or blinking colon separates hours and minutes

• Seconds display either continuously or on a sub-screen (model dependent)

2. Calendar Mode

• Displays the current day of the week and date (MM-DD)

• No leap-year or month-end auto-correction—requires manual adjustment

• Day and date appear in a clean scrolling or side-by-side format depending on the model

3. Alarm Mode

• One daily alarm settable by hour and minute

• Piezo buzzer produces a soft, distinctive tone

• Alarm ON/OFF toggle via button

• Alarm icon appears on-screen when active

4. Hourly Chime

• Optional chime on the hour

• Chime status indicated by icon

• Set or toggled within alarm or time mode

Button Layout (Typical)

Most Seiko A628A watches feature four flat buttons, often labeled on the bezel:

• Button A (Top Left) – Mode cycle (Time → Calendar → Alarm → Chime)

• Button B (Bottom Left) – Set/select digit

• Button C (Top Right) – Increase value

• Button D (Bottom Right) – Confirm setting or toggle functions

The buttons are designed for easy operation without requiring a manual.

Setting Instructions

To set time, date, or alarm:

1. Enter the appropriate mode using Button A

2. Press and hold Button B to enter setting mode

3. Use Button C to adjust the selected value

4. Press Button B again to move to the next field

5. Press Button A to save and exit

The chime and alarm can be toggled using Button D in their respective modes.

Battery Replacement and AC Reset

An AC reset is required after battery replacement.

Reset Steps:

1. Open the case back using a proper tool

2. Remove the old SR1120W battery with plastic tweezers

3. Insert a fresh battery and check for correct polarity

4. Locate the AC (All Clear) terminal on the PCB (typically marked)

5. Short the AC terminal to the battery’s negative terminal (case or spring) for 1–2 seconds

6. LCD should flash, then return to the default time display

Without this reset, the display may remain blank or frozen.

Maintenance Tips

• No lubrication required – fully electronic design

• Avoid moisture—most A628A watches are not water-resistant

• Clean buzzer contact if alarm weakens

• LCDs may develop segment loss with age—repair typically involves replacing the entire module

• If buttons become sticky, open the case and clean contacts with isopropyl alcohol

Watch Models and Design

Seiko used the A628A in a series of “TV-style” digital watches, typically featuring:

• Rectangular, landscape-oriented stainless steel or chrome-plated cases

• Wide metal bracelets

• Model numbers like A628-5000, A628-501A, etc.

• Some dials featured labels like “TV Watch” or “Dot Matrix Display”

These watches were marketed globally and became iconic among digital design enthusiasts.

Conclusion

The Seiko A628A is a standout in the brand’s digital catalog, notable for its distinctive dot-matrix horizontal display and stylish, tech-forward design. With practical features like alarm and calendar wrapped in a futuristic form, it perfectly captures the spirit of early 1980s digital innovation. Today, it's considered a collector’s gem for fans of retro-futuristic design and early digital LCD craftsmanship.