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Fixing a Seiko leaf shutter: putting the shutter blades back in place

The Fuji CW 90mm f/8 lens was the first lens I got in addition to the Rodenstock Sironar-N 150 mm that I got with the camera. Not too long ago, two of the shutter blades got dislodged and I was left with a broken shutter. Instead of spending the price I paid for the lens on a professional repair job, I decided to open it up and carefully see if this was something I could fix myself. As it turns out: I could, and I did. In today’s post, I describe the process and my lessons learnt. I took way too few pictures for this to become a repair guide, but I will give you some pointers for those that want to try this or other shutter repair jobs themselves.

The problem with the shutter is clearly visible once the lens groups are removed. Figure 1 shows the horrific sight of a shutter that has 2 blades completely loose. When you shake the shutter you can hear them move around.

Figure 1: After removing the front lens group, the shutter blades are visible. Two blades have been dislodged and are now loose in the shutter.

For most popular leaf shutters service manuals or videos are available on the web that outline common repairs. For Seiko shutters, unfortunately, there are not that many. Luckily, they are similar in design to the german Prontor and Compur shutters and the folks of the YouTube channel “Fix Old Cameras” have a video on one of those. The model shown in the video is actually more complex than the Seiko shutter I had on the table. The shown shutter has a self timer function and contains another set of gears. The space occupied by that gear train is empty in the Seiko shutter. Also, the Seiko has no T mode and is also missing the lever to hold the lens open for focusing. It had this originally, but that was removed by a professional when the shutter got its first CLA. A simple cleaning job wouldn’t fix the slow shutter problem I was having at that time, and the gear box controlling the shutter timings had to be replaced. The replacement did not support this lever, so it was removed.

Also from the same channel, I recommend you watch this video to get an impression of what these shutters look like on the inside. In the linked video a Copal shutter is opened up, but the general principles are similar across brands and models. Other useful references are this document on the anatomy of Seiko shutters, this thread on the rangefinder forums, and the Mamiya Seiko Parts Catalog provided by butkus.

To reach the shutter blade sub-assembly, the entire shutter has to be opened up on both front and back sides. By removing the set screw, the fastening ring that is visible in Figure 1 can be removed. This ring pre-stresses the face plate, the silver shutter speed selector ring and black selector ring underneath to keep them into place. The latter one forms an assembly with the silver selector ring and they mesh together using a notch (see Figure 2, lower right). All three discs can be removed. Figure 2 shows the shutter with the the black selector ring still in place.

Figure 2: The face plate and silver shutter speed selector ring have been removed. The black selector plate is still visible. When the selector ring is rotated, the visible pins follow the slots and push gears into place.

Once all three are removed, the shutter mechanism is visible. The black cocking ring in the center interfaces with a small gear that is connected to the gear box (hidden from view by a cover plate here, top right). On the top left, we see the release lever. If you flip the entire shutter upside down, three screws are visible that hold the aperture selector in place. After removing these, the ring can be taken off and four more screws become visible. By removing those, the entire assembly shown in Figure 3 can be lifted out of the housing.

Figure 3: Shutter mechanism

On the backside of the assembly, several pins are visible (not shown, this is where I focused on putting the blades back in place rather than on taking photos to document it). Each blade has a slot hole and a pivot hole that fit together with two pins. Figure 4 shows this geometry and how the blades are to be installed. With a little encouragement and several attempts to strain my patience, the blades are put in place. The housing is then replaced upside down, and the four mounting screws are tightened. This fixes the blades in place. It was this point, where a few pieces fell out inadvertently from the mechanism.

Figure 4: Excerpt from the Mamiya repair manual for Seiko shutters. Shown are the way the blades are installed and their layout. Each blade has a pivot and a slot hole.

If you compare Figures 3 and 5 you will see that the release lever and the cocking rings are missing. In Figure 5, I have already placed two other levers back into their right locations.

Figure 5: After flipping the shutter to reach the aperture ring, three levers and springs fell out.

This is where taking detailed photographs comes in handy. A detailed view of the mechanism is depicted in Figure 6. The orientation of several levers and their pretensioning springs are included. The spring that pretensions the release lever has to be seated in a little cutout in the lever underneath and against the wall of the casing. The spring is, however, mounted on the underside of the lever, and can easily drop out. A pair of tweezers are essential to replace this assembly correctly, and you will need both hands to manipulate all the levers and springs, while holding the other one in place. I used one pair of tweezers to clamp the spring against the release lever, so that it would stay put until the assembly was placed correctly.

Figure 6: Detail view of how the three missing parts fit together and points of attention.

It took a few tries, but after closing up the shutter it fires correctly again.

So, what to look out for when attempting this yourself?

  1. Make pictures of every step and under various angles. Sometimes important details are hidden from view, but become clear from viewing the assembly under a different angle. If you think you have sufficient pictures, go ahead and take some more.
  2. A lot of the screws are tiny, and of different threads and lengths. Catalog them and keep them safe. They are not interchangeable.
  3. You do not need a lot of torque to loosen or fasten the screws. Do not force it, or you will run the risk of stripping the threads.
  4. Take your time. These repairs take patience and dexterity. Sometimes you need to play with it for a while, to find the best way of approaching the problem. Especially in placing parts back, it may be that only one sequence of manipulations works well.

Good luck!

Published in DIY Large Format Photography