The Seiko A826A is a specialized digital quartz LCD movement introduced in the 1980s, primarily designed for diver’s watches. It powers some of Seiko’s earliest professional diving computers—notably models with depth sensors, dive timers, and enhanced underwater readability. The A826A is a rugged, purpose-built movement that combines standard digital timekeeping with critical diving functions, making it a pioneering module in the realm of analog-digital hybrid tool watches.

Technical Specifications

• Caliber Number: A826A

• Movement Type: Quartz (Digital LCD)

• Display Type: Multi-field Liquid Crystal Display (with segment and bar graph readouts)

• Primary Functions:

  • 12-hour Timekeeping

  • Day and Date Calendar

  • Daily Alarm

  • Dive Timer (Max Depth, Dive Duration, Current Depth)

  • Surface Interval Indicator

  • Depth Sensor Interface

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

• Depth Sensor: Integrated via case-mounted pressure sensor

• Backlight: Electroluminescent or case-mounted external lamp (model-dependent)

• Battery Type: CR2025 lithium coin cell

• Battery Life: ~2–3 years (depending on dive and light use)

• Accuracy: ±20 seconds per month

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

• Module Dimensions:

  • Diameter: ~30 mm

  • Depth: ~6–7 mm (to accommodate sensor interface)

Display and Dive-Oriented Features

The Seiko A826A’s LCD was uniquely tailored for underwater operation and high-contrast visibility:

• Main Digital Display:

  • Time in HH:MM format (with seconds displayed separately)

  • Dive duration timer

  • Max depth and current depth readouts during a dive

  • Post-dive surface interval counter

• Bar Graph:

  • Visual representation of depth in meters

  • Acts as a quick-glance safety reference during ascent/descent

The screen is typically shielded by a sapphire or mineral crystal and surrounded by a thick shroud or bezel for extra durability.

Operating Modes

The A826A supports multiple dedicated modes suited to divers and professionals:

1. Timekeeping Mode

• Standard time display with seconds

• 12-hour format with PM indicator

• Displays day of the week and date

2. Calendar Mode

• Shows day and date (MM-DD or DD-MM depending on market)

• No year tracking

• Manual adjustment required for shorter months

3. Alarm Mode

• One daily alarm

• Set by hour and minute

• Audible underwater piezo buzzer (muted automatically during dive mode)

4. Dive Mode (Auto-Activated Underwater)

• Activated automatically below 1.5 meters

• Displays:

  • Elapsed Dive Time

  • Maximum Depth Reached

  • Current Depth (in real time)

• Records dive log data for later reference

• Includes ascent speed warnings on some versions

5. Surface Interval Tracking

• Once dive ends, surface interval time starts

• Encourages proper rest and safety between dives

Button Layout

Watches with the A826A typically feature four or five pushers, designed for use with gloved hands:

• Mode Button – Cycles through time, alarm, and calendar

• Set Button – Initiates setting modes

• Advance Button – Adjusts values

• Light Button – Activates backlight (on equipped models)

• Dive Data Recall (optional) – Shows previous dive stats

Buttons are large, knurled, and pressure-tested to ensure function underwater.

Setting Instructions

To set the time or alarm:

1. Press the Mode button to enter time or alarm mode

2. Hold the Set button until the digits flash

3. Use the Advance button to change the hour/minute

4. Press Set to confirm

5. Use Mode to return to standard display

Alarm can be toggled ON/OFF with a short press in alarm mode.

Battery Replacement and Caution

Battery Notes:

• Use only CR2025 lithium battery

• Replace battery at service intervals recommended for diver’s watches

• Always perform water resistance testing after resealing case

AC Reset:

The A826A may require a full AC reset after battery change:

1. Locate AC terminal on the module

2. Short the AC point to the battery’s negative terminal (typically case or spring contact)

3. Use metal tweezers for 1–2 seconds

4. Watch will reset and return to time mode

Skipping reset may lead to blank screen or failure to detect depth properly.

Maintenance and Service

• Annual or biannual pressure testing recommended

• Avoid pressing buttons underwater unless watch is rated for that use

• Clean depth sensor port to prevent salt buildup

• Store in dry, cool environment when not in use

• Replace gaskets during battery change for ongoing water resistance

Watch Models Using A826A

Most notably used in:

• Seiko A826-6019 and A826-6000 "Diver's Computer" models

• Integrated depth sensor design

• Prominent external bezel

• “Diver’s 150M” or “200M” printed on dial

These watches became popular among professional divers and are now highly collectible for their early dive computer functionality.

Conclusion

The Seiko A826A movement is a remarkable example of Seiko’s innovation in digital dive watch technology. With its automatic dive timer, depth tracking, and rugged construction, it served as a precursor to the modern dive computer. Today, A826A-equipped watches remain highly sought after by collectors, adventurers, and enthusiasts who appreciate true tool-watch engineering from Seiko’s golden era.