The Seiko A827A is a professional-grade digital quartz LCD movement developed in the mid-to-late 1980s. It powered Seiko’s wrist dive computers—specifically models in the Scuba Master series, such as the A827-6010 and A827-6019. As a direct evolution of the A826A, this module integrated depth sensing, dive timing, and surface interval tracking, making it one of Seiko’s most iconic digital tools for divers. The A827A was designed for extreme environments, with rugged waterproof cases and a user-friendly layout suited for underwater visibility and operation.

Technical Specifications

• Caliber Number: A827A

• Movement Type: Quartz (Digital LCD with depth sensor)

• Display Type: Segmented Liquid Crystal Display (7-segment + bar graph)

• Primary Functions:

  • 12-hour timekeeping

  • Calendar (Day and Date)

  • Daily Alarm

  • Dive timer

  • Depth measurement (Current & Max)

  • Surface interval timer

  • Automatic dive log memory

• Time Format: 12-hour (AM/PM indicator)

• Depth Range: 0–80 meters

• Resolution:

  • 0.1 m (0–10 m)

  • 0.5 m (10–80 m)

• Backlight: External case-mounted lamp (varies by model)

• Battery Type: CR2025 (3V lithium)

• Battery Life: Approx. 2 years

• Accuracy: ±20 seconds/month

• Water Resistance: 150m or 200m depending on model

• Module Diameter: ~30 mm

• Module Depth: ~6–7 mm

Display Layout

The A827A features a horizontal digital layout optimized for diving conditions, glove use, and quick visibility underwater.

LCD Readout:

• Top Line:

  • Day of week (MO, TU, etc.)

  • Mode indicators: “DIVE”, “AL”, “PM”

  • Max depth reading or dive recall icon

• Main Area:

  • HH:MM:SS in time mode

  • Dive duration during active dive

  • Current depth in meters

  • Surface interval timer (post-dive)

• Bar Graph:

  • Visual display of current depth

  • Helps monitor safe ascent speed

This layout made the A827A ideal for divers who needed real-time data without toggling through screens.

Operating Modes

The A827A offers five core modes:

1. Timekeeping Mode

• Standard 12-hour clock

• PM indicator appears for post-noon hours

• Seconds continuously count

2. Calendar Mode

• Day and numeric date display

• No year/leap year tracking

• Manual correction required for month-end

3. Alarm Mode

• One daily alarm

• Hour and minute setting

• “AL” icon appears when active

• Audible piezo buzzer alert

4. Dive Mode (Auto-Activate)

• Automatically starts when submerged below ~1.5 meters

• Displays:

  • Elapsed dive time

  • Current depth

  • Max depth

• Timer pauses when diver returns to surface

• Lockout prevents accidental resets during dive

5. Surface Interval Timer

• Begins once diver surfaces

• Helps enforce recommended decompression intervals

• Clears after a set time or when a new dive starts

Dive Memory / Recall

The A827A stores the last dive's data, including:

• Max depth

• Total dive time

• Surface interval duration

These are accessible via a RECALL button on the case, allowing users to review past dive performance.

Button Layout

Most watches using the A827A feature five buttons:

• Mode Button – Cycle through time, alarm, calendar, recall

• Set Button – Initiates setting mode

• Advance Button – Adjust values

• Light Button – Activates external lamp (on equipped models)

• Recall Button – Displays last dive’s memory (depth, duration)

Button size and resistance were designed with glove use in mind, often with tactile feedback for underwater operation.

Battery Replacement & AC Reset

After a battery change, an AC (All Clear) reset is required to reinitialize the circuit.

AC Reset Steps:

1. Open the case back using the appropriate tool

2. Remove the spent CR2025 lithium cell

3. Insert a fresh battery with correct polarity

4. Locate the AC terminal on the circuit board

5. Use metal tweezers to short the AC contact to the battery’s negative terminal (case or spring contact)

6. LCD should flash all segments, then reset to time mode

Always pressure-test after resealing to ensure water resistance.

Maintenance & Use Tips

• Rinse thoroughly in fresh water after each saltwater dive

• Do not press buttons underwater unless specified

• Clean depth sensor regularly with soft brush

• Store dry and flat when not in use

• Replace case gaskets at each battery change

• Recommended to pressure test annually if used for diving

Watch Models Using A827A

Most iconic example:

• Seiko A827-6010 / A827-6019 “Scuba Master”

  • Large stainless steel case with external sensor port

  • Rubber or stainless integrated straps

  • Bezel often labeled with “Diver’s 200m”

  • Prominent “DIVE” and “LOG” indicators

These watches are now highly collectible and are considered precursors to modern dive computers.

Conclusion

The Seiko A827A movement represents a milestone in wrist-worn dive instrumentation. It provided reliable depth tracking, automatic dive logging, and essential timing functions in a rugged case designed for real-world underwater use. Decades later, it remains a landmark achievement in Seiko’s digital history—sought after by tool watch collectors, divers, and vintage Seiko fans alike.