Seiko Caliber 7x52a

Seiko Caliber 7X52

Seiko Caliber 7x52

Brand Seiko
Caliber Number 7X52, 7X52A
Movement Type Quartz, Solar Powered
Jewels 10
Crystal Oscillator Frequency
32,768 Hz (cycles per second)
Driving System
Step motor
CLB2016 (3.7V)
Functions Automatic GPS time setting, date, dual-time, in-flight mode
Country of Manufacture Japan
Known Models SAST005, SAST007, SAST015

The Seiko caliber 7x52A is found in the first generation of Astron watches.

Detailed Features:

  • GPS controlled time and time zone adjustment
  • Perpetual calendar correct to February 2100
  • Signal reception result indication
  • World time function (39 Time Zones)
  • Daylight Saving Time function
  • Power save function


Seiko claim the accuracy of the 7X52 in normal conditions is +/- 15 seconds per month.

Charging Time

The Seiko caliber 7X52 requires more energy than other solar watches because of the GPS signal reception. The charging time depends on the light source and how how much light is emitted, measured in LUX. The higher the LUX the faster the charge. For example, charging in the sunlight will be faster than using a standard light bulb.

  • 3,000 LUX florescent bulb takes ~530 hours to fully charge
  • Daylight on a cloudy day takes ~135 hours to fully charge
  • Sunlight on a sunny day takes ~65 hours to fully charge

Power Reserve

It literally takes days to charge the Astron, however, when fully charged the caliber 7X52A has a power reserve of about 6 months.

Note: when charging your watch in the sunlight, make sure that the temperature is not too hot or it can damage the dial, solar cell, or other parts of the watch. Always keep the watch temp below 60 C.

Can you wear it while charging?

You can wear your watch while it has low power or while it is charging, however, it may slow down the charging time if your watch is under your sleeve or not in direct light.

Can you overcharge it?

The Seiko caliber 7X52 has an overcharge prevention function to make sure your watch will not be over charged.

Low Power Indicator

The Seiko 7X52 has several series of low power warnings:

  • Second hand ticks every 2 seconds: The watch will still tell the time, but the GPS automatic time setting will not work until it is charged.
  • Second hand ticks every 5 seconds: The watch will stop telling the time and the GPS will not function until it is charged.

From Seiko

While the watch is being charged, the second hand moves at “ 5-second Intervals.” During the “5-second Interval Movement,” neither the buttons nor the crown can be operated.

2 Power Save functions

The second hand has stopped at the 15 seconds mark: Power Save 1 function has been activated. The time display will stop and the time cannot be set until the watch is charged. This Power Save setting can be initiated with as little as 72 hours without a sufficient light source.

The second hand is pointing to the 45 seconds mark: Power Save 2 has been activated. The time will stop and the date will display 1. The time cannot be set until the watch is charged. This Power Save setting is initiated when the watch is in storage or without a light source for a long period of time.

Rechargeable Capacitor

The capacitor (secondary battery) that is installed from the factory is a 3.7V rechargeable cell. The number is CLB2016. Also stamped on the cell is 12 and 63M. This oem part is manufactured by Maxwell in Japan, however, similar cells from other manufacturers will work fine.

Seiko Caliber 7x52 Clb2016 Capacitor

Replacing the Capacitor

Capactitors do not last forever. Sometimes they will need changed. According to the notice on the battery cover, when replacing the cell you must “short AC and + of the battery”. Do not try to fit a standard battery.

Seiko Caliber 7x52a Battery

From Seiko

The battery used in this watch is a special secondary battery, which is different from ordinary batteries. Unlike an ordinary silver oxide battery, the secondary battery does not require periodic replacement. The capacity or charging efficiency may gradually lower due to long-term use or operating environment. In addition, long-term use may shorten the charge duration due to wear, contamination, lubricant deterioration of mechanical parts, etc. Request repair when the performance lowers.

Examples of watches with this movement

Seiko Astron Sast007 7x52Seiko Astron Sse060 7x52Seiko Astron Sast009 7x52

Additional Resources


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Hi guys, I’m confused by this one. Is it quartz or solar powered? Love the site by the way!


Where can I find a battery for this model?


[…] The Seiko Astron models feature similar functionality, check out the caliber 7X52 here. […]

Benny D
Benny D

I have an Astron that I bought when it first came out but it has been in my drawer for the past 8 months and lost all power. It would not move at all until I put it on the window for a week. Does anyone know of a faster way to charge these?


Sun during day, led lamp at night

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