Seiko 7S26 Movement (Everything You Need to Know)

Manufacturer	Seiko
Caliber Number	7S26
Movement Type	Automatic
Diameter	27.4mm
Casing Diameter	27mm
Height	4.8mm
Jewels	21
Hacking	No
Hand-winding	No
Vibrations per hour	21,600 bph
Shock System	Seiko Diashock
Regulator	Etachron
Power Reserve	~41 hours
Magnetic Resistance	4,800 A/m (60 gauss)
Winding Direction	Bi-directional (Magic lever)
Country of Manufacture	Japan/Malaysia/Singapore
Known Watches	Seiko 5, Seiko SKX, Seiko Monster, etc.

The Seiko 7S26 movement is an automatic movement used in many popular Seiko dive watches, such as the Seiko SKX, Monster, and entry-level Seiko 5 watches.

The 7S26 has 21 jewels, a power reserve of ~41 hours, and a reported accuracy of  -20 to +40 seconds per day.

Discontinued 7S26

The 7S26 was first released in 1996, but its production has since been discontinued. The 7S26 movement can still be found available inside of earlier, entry-level Seiko 5 watches, such as the SNK809.

Newer entry-level Seiko watches, including the recently updated Seiko 5 Sports lineup, instead use the upgraded caliber 4R36 movement with hacking and hand-winding. 

Setting the Time

In order to set the time on the 7S26:

1. Pull the crown out to position 2, two clicks away from the case. On a dive watch with a screw-down crown, such as the Seiko SKX, you must first unscrew the crown by rotating it counter-clockwise.
2. Rotate the crown, clockwise or counter-clockwise, until you set the hour and minute hands to the designated time.
3. Push the crown back in toward the watch’s case until you feel it “click”. And voila, you have successfully set the time.

Setting the Day and Date

Note: Seiko suggests that you do NOT adjust the date while the movement is in the middle of changing the date. This happens between 9:00 PM and 4:00 AM. Ignoring this may damage the movement. A trick to always avoid this is to first set the watch’s time to 6:30, AM or PM, as putting both hands at 6:30 will move them away from the ‘danger zone’.

In order to set the day and date on the 7S26:

1. Pull the crown out to position 1, one click away from the case.
2. Rotate the crown forward (clockwise) to change the date.
3. Rotate the crown backward (counter-clockwise) to change the day.
4. Once the day and date are set, push the crown back into position 0 (nearest to the case) to complete the process.

Check out the video below to learn how to set the Time/Day/Date on a Seiko SKX that uses the 7S26 movement.

Servicing the 7S26

The 7S26 movement is well-reported to keep running for 5 – 25 years without needing a service. This is likely due to the inclusion of plastic parts that don’t require as much lubrication to keep the movement maintained and running smoothly.

I own a Seiko 5 from 1989, passed down from my late grandfather, that houses a Seiko 7009 movement. which the 7S26 replaced. The Seiko 5 has never been serviced, and still runs and keeps time perfectly. The day-date wheel is no longer functioning, however.

With that said, if you do find your 7S26 movement is due for a service, as it is no longer working, or keeping time well outside of its reported accuracy of -20 to +40 seconds per day, it may be unwise to get it serviced by a watchmaker, as a service will likely cost more than a new movement, and in some cases, the entire watch. Further, since the 7S26 has been discontinued, the movement has continued to rise in price, often fetching between $60 – $80.

Check out the video below for a complete breakdown and repair of the 7S26 movement.

Replacing the 7S26 With the NH36A

Instead of servicing the antiquated 7S26 which is not very cost-efficient, many 7S26 owners opt to simply replace the movement with an upgraded NH36A movement (check price).

The NH36A movement is newer, more affordable, and more widely available than the 7S26. It also has additional hacking and hand-winding features, making it a very popular choice for Seiko watch modders.

Check out the video below for a tutorial on how to replace the 7S26 with an NH36A movement.

Seiko’s Anti-Shock Diashock System

The 7S26 uses Seiko’s proprietary diashock anti-shock system. This is what makes the 7S26 such a durable workhorse movement, resistant to damage from drops, bumps, and falls.

I can attest to the effectiveness of the diashock system first-hand, as I’ve owned many Seiko 5s and have not babied them at all. They’ve been with me on many adventures, including activities where they’ve been bumped, dropped, etc, and are all still running effectively.

7S26A vs 7S26B vs 7S26C

7S26A vs 7S26B

Over time, the 7S26 movement has faced three distinct evolutions, the 7S26A, 7S26B, and 7S26C. The 7S26 and 7S26A are the same, the first generation.

The 7S26B was released along with the 7S36B in 2006. According to Seiko, the difference between the 7S26A and 7S26B relates to the design of the balance staff, and its repairability. This allows for greater precision in the watch’s timekeeping once set properly.

7S26B vs 7S26C

The 7S26C was released then released in 2011 in conjunction with the 7S36C.

According to Seiko, the 7S26C was constructed the same as the 7S26B, but using new parts. Since the size of the movement is exactly the same, either movement could be used interchangeably in any watch that accepts them, however, parts between these movements are not interchangeable (source).

7S26 vs 4R36

The 7S26 is no longer used by Seiko, replaced by the 4R36 in newer, entry-level models, such as their Seiko 5 Sports lineup.

One of the main upgrades in the 4R36 is the addition of hacking and hand-winding functionalities. Hacking allows you to pull out the crown to stop the second hand while setting the time. Hand-winding allows you to power the mechanical movement by winding the crown, which is especially useful to give your mechanical watch a full charge before taking it off, so it is hopefully still running the next time you wear it.

Seiko claims that the accuracy of the 4R36 is between -35 to +45 seconds per day, however, I’ve experienced greater accuracy on my Seiko 5 Sports models that use the 4R36. One of my 4R36 Seiko 5s, the SRPH29, runs at about +5 seconds per day, while my Seiko 5 Sports SRPD95 comes in at +9 seconds per day.

7S26 vs NH35/NH36

The NH35 and NH36 movements are Seiko-built automatic movements, equivalent to the 4R35/4R36, that are often sold to, and used by other watch manufacturers. Popularly, Invicta has used the NH35A in their Invicta Pro Divers.

The NH35 only features a date complication, while the NH36 features both day and date. Aside from branding, the NH35/NH36 are designed and functionally similar to the 4R3X (4R35/4R36) series of movements in every other way.

7S26 vs 7S36

The 7S36 is Seiko’s latest, and last 7S movement. It’s identical to the 7S26 in all ways, except for 2 additional jewels, for a total of 23 jewels, while the 7s26 only has 21.

Watches That Use the 7S26

The 7S26 movement is found most often in Seiko’s discontinued divers, such as the Seiko SKX, and Seiko’s entry-level Seiko 5 models.

Personally, I have owned watches such as the SNK809, SNK803, SKX007, SKX009, SNKL41, SNXS79, and a few more that I’m sure I’m forgetting, all of which use the 7S26 movement. Almost 6 years later, none of them have let me down, nor needed a service. While not the most precise timekeepers on the planet, they sure are durable and have survived anything I’ve thrown at them.

Other watches that use the 7S26 include:

• Seiko 5
  • SNK809, SNK807, SNK805, SNK803
  • SNXS79, SNXS77
  • SNKL23, SNKL15
  • SNK795, SNK789
  • SNKL41, SNKL41
• Seiko Recraft
  • SNKP27, SNKN37, SNKP23, SNKM97
• Seiko SKX
  • SKX007, SKX009, SKX013
• Seiko Monster 1st Generation
  • SKX779, SKX781

Conclusion

The Seiko 7S26 movement is a tried and true, entry-level affordable movement that has been a staple in Seiko’s affordable lineup for years. The movement is discontinued, and Seiko’s entry-level models instead now use the newer, upgraded 4R36, with hacking and hand-winding, as seen in their new Seiko 5 Sports lineup.