The Seiko A826A is a specialized digital quartz LCD movement developed in the mid-1980s to power Seiko’s early diver’s computer watches. Most notably, it was used in the Seiko Scuba Master series. The A826A is designed for underwater functionality, offering depth measurement, dive timing, and surface interval tracking, all automatically triggered upon submersion. This made the A826A one of the earliest wrist-worn digital dive computers available to recreational and professional divers alike.

Technical Specifications

• Caliber Number: A826A

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

• Display Type: Multi-field 7-segment LCD with graphical elements

• Primary Functions:

  • 12-hour timekeeping (AM/PM)

  • Calendar (Day and Date)

  • Daily alarm

  • Dive mode (auto-activated)

  • Depth measurement (current & max)

  • Dive timer

  • Surface interval tracking

• Depth Measurement Range: 0–80 meters

• Resolution: 0.1 m (0–10 m), 0.5 m (10–80 m)

• Backlight: Not integrated (some cases included external lamp)

• Battery Type: CR2025 lithium cell

• Battery Life: ~2 years (may vary with dive/light usage)

• Accuracy: ±20 seconds per month

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

• Module Diameter: ~30 mm

• Module Thickness: ~6–7 mm

Display and Layout

The A826A features a robust, high-visibility horizontal LCD layout, ideal for underwater viewing.

Display Elements:

• Top Section:

  • Day of the week

  • Function indicators (e.g., AL, DIVE, PM)

• Main Readout Area:

  • Time: HH:MM:SS (in normal mode)

  • Dive timer: minutes and seconds

  • Depth (in meters) during dive

  • Max depth memory

  • Surface interval timer after surfacing

• Graphical Bar Scale:

  • Displays approximate depth range as a visual bar (useful for glancing)

This layout is designed to deliver key information at a glance, even in low-visibility underwater environments.

Functional Modes

1. Timekeeping Mode

• Displays time in 12-hour format

• PM indicator shows for post-noon hours

• Seconds always visible

2. Calendar Mode

• Displays day and date

• Format varies by region (MM-DD or DD-MM)

• Manual correction required for shorter months

3. Alarm Mode

• Single daily alarm

• ON/OFF toggle

• “AL” icon shows when alarm is active

• Audible signal via piezo buzzer

4. Dive Mode (Auto-Activated)

• Automatically engages when submerged >1.5 meters

• Displays current depth, dive time, and max depth

• Dive time measured from immersion

• Max depth recorded during session

• Surface interval tracked after ascent

• Dive data retained until next dive

5. Recall Mode (Dive Log)

• Some models store last dive data

• Press specific button to recall max depth and dive time after surfacing

Button Layout (Typical)

Seiko A826A watches generally include four to five side buttons:

• Mode Button – Cycles through Time, Alarm, Calendar, and Recall

• Set Button – Enters setting mode

• Advance Button – Adjusts values

• Light Button – Activates lamp (model-dependent)

• Dive Data Recall Button – Displays stored dive info

Buttons are large, easy to press, and designed for gloved use.

Setting Instructions

Setting the Time:

1. Press Mode to enter time mode

2. Press and hold Set until hours flash

3. Use Advance to increase digits

4. Press Set again to switch to minutes and seconds

5. Press Mode to confirm

Setting the Alarm:

1. Enter alarm mode via Mode button

2. Hold Set until hour blinks

3. Adjust hour/minute using Advance

4. Toggle alarm ON/OFF with a short press of Advance in alarm mode

Battery Replacement and AC Reset

After battery change, the module requires a full reset.

AC Reset Procedure:

1. Open case back using appropriate tool

2. Remove the old CR2025 lithium battery

3. Insert new battery, observing correct polarity

4. Locate the AC terminal (marked on PCB)

5. Short AC terminal to battery’s negative terminal (case or spring) with metal tweezers for 2–3 seconds

6. Display will reset and return to time mode

Warning: Always perform water-resistance testing after battery replacement.

Maintenance Tips

• Rinse with fresh water after saltwater dives

• Avoid pressing buttons underwater unless specified

• Clean sensor port regularly to prevent salt buildup

• Replace gaskets during battery change for water resistance

• Schedule pressure testing annually if used for diving

• Avoid extreme heat or magnetic fields

Watch Models Using A826A

Most famously used in:

• Seiko Scuba Master A826-6000 / A826-6019

• Integrated depth sensor on side of case

• Large rectangular stainless steel case with rubber or steel strap

• Labeled bezel and DIVE indicator on dial

• Highly collectible and considered a precursor to wrist-mounted dive computers

Conclusion

The Seiko A826A movement marked a turning point in wearable dive technology. With automatic dive mode, depth tracking, and surface interval features, it bridged the gap between digital wristwatches and modern dive computers. Today, A826A-powered watches remain iconic for their durability, functionality, and pioneering spirit in underwater instrumentation—making them a favorite among vintage Seiko collectors and serious dive watch enthusiasts.