Master Watchmaker, Clockmaker and Jeweller (since 1981)
rolex omega panerai iwc patek and other fine watches by Nicholas Hacko Sydney
Suite 403, Level 4, Culwulla Chambers
67 Castlereagh St. Sydney 2000 NSW Australia
Phone: (02) 9232 0500     Fax: 02 9233 2273

Do It Yourself Project: Seiko 7S26 for Novice Horologists

Chapter 6: Disassembly - case / bracelet / movement extraction

My Seiko 5 has finally arrived! On the same day I also received the basic tool kit.

Seiko 5 - DIY Project

The watch arrived from Singapore exactly 10 days after placing an order on eBay. It was neatly packed, in original Seiko box.

Seiko 7S26 DIY Repair Project

Model reference: 7S26-02E0 (also known as SNK639K1).

Seiko 7S26 DIY Assembly and Disassembly - Seiko 7S26-02E0

7S26 Repair Project

Let's get into it!

Tools: Case holder, case opener, screwdriver (60 or 0.6mm and 100 or 1 mm), tweezers.

Seiko 7S26 bracelet removal

1. Bracelet removal

The very first step is to detach the bracelet from the watch case. Note how the bracelet is positioned: the Seiko logo on the clasp is "facing" the 6 o'clock position.

Seiko 7S26 bracelet - spring loaded bar

Gently press the spring loaded bar in and pull the bracelet away. If necessary, push the bar form the other side too.

Seiko 7S26 DIY project - clasp

Here is another shot of the spring loaded bar (clasp)

Seiko 7S26 bracelet and clasp detachment

Now detach the bracelet from the watch case by sliding down the spring loaded bar (screwdriver size 100 or 1 mm blade).

Seiko DIY bracelet removal with size 100 screwdriver

Note that this bar is slightly different than a clasp bar - it has two "shoulders". Place the screwdriver between the two shoulders as per photo, slide the bar while pushing the bracelet towards yourself, away from the case. NOTE: I am left handed, so you need to rotate the watch to suit you. Here is another shot of the bar, showing the position between the shoulders where you should place the screwdriver (size 100) .

Seiko 7S26 bracelet end pieces

Reassemble the bracelet and store the two end pieces and bars in a plastic bag. If you are working on a pre-owned/used watch, clean the bracelet with warm soapy water. To clean the bracelet use dishwashing liquid and tooth brush. If necessary, soak overnight first. Dry well with a hair dryer.

Seiko 7S26 bracelet removal

Case back removal

Place the watch in the case holder as per photo. Close the holder as high as you can for a firm grip. The 3 arrows mark position on the case back where prongs of the case opener will be inserted.

Seiko 7S26 DIY case back removal

However make sure that the watch sits parallel and in level, not under angle.

Seiko 7S26 case on case holder

Here is another shot showing the point of rest / contact between the case and the tool:

Seiko 7S26 case back removal

Adjust the 3 prongs of the case removal tool so that the prongs are gripping the watch case back firmly. Use a rolling screw on the top to close the first 2 prongs and then rotate handle bar to bring the third prong. Proper alignment is absolutely crucial! Take your time to adjust the tool so that both grip and alignment are correct.

Using case removal tool with Seiko 7S26

Here is another shot of the case opener showing correct alignment and grip. If your case opener comes with multiple attachments, use the finest, most pointy one.

Removing the case of a Seiko 7S26 with case back removal tool

To open: put enough down pressure on the tool so it wont slip ! Turn the handle counter clock wise. Once the case back gets reasonably lose, remove the tool and unscrew it by hand.

Important note: once again, it is absolutely crucial that the tool, case holder and the watch itself are properly aligned and parallel. In most cases the case back will open relatively easily. However in the case of a divers watches, it is a good idea to clamp the case holder in with a large vice. By doing so, you will have both hands free to hold and press down the case opener. Water damaged cases are almost impossible to open by hand. You may need a large bench case opener.

DIY Seiko 7S26 Sydney

DIY Seiko 7S26

WARNING! It is ABSOLUTELY CRUCIAL that after removing the case back you DO NOT TOUCH any parts - either by hand or by a tool - which located in / around balance wheel section, especially not the balance wheel, hair spring or regulators ! ! !

Seiko 7S26 DIY - with case back removed

Gently and carefully remove the case back seal. DO NOT STRETCH IT! Old watches: most likely the case seal has lost it's elasticity and would require replacement. Still, try not to break it!

Seiko case seal and case back

Movement (mechanism) extraction

In order to extract the movement, you need to remove the winding stem. Refer to the Technical guide, page 9 section 6. Locate the setting lever (part number 0383 070, item 39)

DIY Seiko 7S26 winding stem

Push the setting lever with tweezers, hold down and pull the stem out.

Seiko DIY - pulling the winding stem out

Photo showing winding stem and crown. Note: the stem is both a movement and case-related component, while the crown and seal are case-related components only.

Seiko DIY winding stem, crown seal and winding crown

Movement extraction: using tweezers as a lever (resting against the watch case) pull the movement straight up (gently!). When extracting, hold oscillating weight (winding rotor) as close to the ball bearing as practically possible.

Seiko 7S26 DIY - oscillating weight with ball bearing

Remove and place on bench, dial and hands UP.

DIY Seiko 7S26 movement extraction

DIY Seiko 7S26 with movement extracted

Photo showing proper way of holding the movement by hand. Do not touch the dial or hands with neither tool nor fingers! Always hold and handle as shown here.

Handling Seiko 7s26 movement

Insert the winding stem and crown into the mechanism (push in slowly and gently, turn stem slightly if required). You don't need to push down the setting lever to re-insert the stem, it will click in automatically. Place the mechanism into the movement holder as shown below.

Seiko 7s26 - reinserting winding stem

DIY Seiko 7S26

With the movement secured in the holder, pull the stem out to check if the time and calendar adjustments are operational.

Troubleshooting tip:
In the unlikely case that the stem is not inserted properly, go back to stem removal procedure, remove it as described above and then re-insert it again. A properly installed stem will "click" into correct position with a gentle push.

This completes the movement extraction procedure. Place all removed parts in a sealed container, ( Leave the movement remaining on the holder) and keep the lot in a dust free environment.

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