The Seiko A827A is a specialized digital quartz movement developed in the 1980s to power Seiko’s first-generation diving computers. Built with a depth sensor interface, this module was at the heart of the iconic Seiko Scuba Master A827-6010, a rugged and innovative tool watch designed for serious underwater use. Combining reliable digital timekeeping with real-time dive data, the A827A remains one of Seiko’s most advanced and collectible LCD dive calibers of its era.

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Technical Specifications

• Caliber Number: A827A

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

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

• Key Functions:

  • 12-hour timekeeping

  • Day and Date calendar

  • Daily alarm

  • Automatic dive mode (with depth measurement)

  • Dive timer

  • Max depth memory

  • Surface interval timer

• Time Format: 12-hour (with PM indicator)

• Depth Range: 0.0 – 80.0 meters

• Depth Resolution:

  • 0.1 m (0–10 m)

  • 0.5 m (10–80 m)

• Backlight: Not integrated (some watches include external light)

• Battery Type: CR2025 (3V lithium coin cell)

• Battery Life: Approx. 2 years

• Accuracy: ±20 seconds/month

• Water Resistance: 150m or 200m (model-specific)

• Module Diameter: ~30 mm

• Thickness: ~6.5 mm

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Display Overview

The A827A features a horizontal layout optimized for quick readability under water.

Display Elements:

• Upper Section:

  • Day of the week (MO, TU, etc.)

  • Function indicators: DIVE, AL, PM

  • Mode-specific symbols

• Main Field:

  • Time: HH:MM:SS

  • Dive duration timer

  • Current depth (in dive mode)

  • Surface interval time

• Bar Graph:

  • Depth visual indicator

  • Useful for monitoring changes at a glance

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Functional Modes

1. Timekeeping Mode

• Standard digital time display

• Seconds count visible

• PM icon appears for afternoon times

2. Calendar Mode

• Day and numerical date

• Format: MM-DD or DD-MM depending on the version

• Manual correction required for month-end

3. Alarm Mode

• One daily alarm

• Settable in hours and minutes

• Toggle ON/OFF

• “AL” icon displays when active

4. Dive Mode (Automatic Activation)

• Activates when submerged to 1.5 meters or deeper

• Automatically begins dive timing

• Displays:

  • Current depth

  • Maximum depth reached

  • Elapsed dive time

• Dive mode locks out non-essential features to prevent accidental inputs

5. Surface Interval Timer

• Starts counting after the diver resurfaces

• Aids decompression awareness

• Resets with each new dive

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Dive Memory & Recall

The A827A stores last dive data automatically, including:

• Max depth

• Dive duration

• Surface interval

You can access this information using the RECALL button after a dive. This feature helps divers track their recent activity and monitor recovery between sessions.

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Button Configuration

Typical A827A-powered watches include five external pushers:

• MODE – Switch between Time, Alarm, Calendar, and Dive Recall

• SET – Enter set mode for time or alarm

• ADJUST – Change values in set mode

• LIGHT – Activates external lamp (if present)

• RECALL – Displays last dive data (depth and duration)

The buttons are deliberately oversized and well-spaced for underwater operation with gloves.

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Setting Instructions

Setting the Time:

1. Press MODE to reach Time mode

2. Hold SET until hours flash

3. Use ADJUST to change value

4. Press SET to cycle to minutes and seconds

5. Press MODE to save and exit

Setting the Alarm:

1. Press MODE to access Alarm mode

2. Hold SET to begin setting

3. Use ADJUST to change hour/minute

4. Use a short press of SET to toggle alarm ON/OFF

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Battery Replacement & AC Reset

After changing the battery, the module must be reset using the AC (All Clear) procedure.

Steps:

1. Open the case back

2. Remove the old CR2025 battery

3. Install a new battery (ensure proper polarity)

4. Locate the AC contact on the circuit board

5. Short the AC point to the battery’s negative terminal using tweezers for 1–2 seconds

6. LCD should reset to time mode

Always pressure-test the watch after servicing to ensure diving suitability.

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Maintenance Tips

• Rinse the watch with fresh water after every saltwater dive

• Do not press buttons underwater unless specified

• Keep depth sensor port clean to ensure accurate readings

• Replace case gaskets during battery service

• Store in a dry environment

• Avoid extreme heat or magnetism

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Known Watch Models

Most famously featured in:

• Seiko A827-6010 / A827-6019 Scuba Master

  • Large stainless steel case

  • External depth sensor

  • Rubber dive strap or integrated bracelet

  • Prominent “DIVE” indicator on bezel or face

These models were marketed as professional dive computers, well ahead of their time.

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Conclusion

The Seiko A827A is a landmark quartz movement in the evolution of wrist-worn dive computers. It provided vital underwater metrics in a robust, user-friendly layout. With its automatic dive activation, depth logging, and surface interval tracking, it brought professional-grade features to the wrist. Today, A827A-equipped watches are highly collectible for both their technical merit and historic importance in dive watch design.

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