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Discussion Starter · #1 ·
I figured it was time to put some myths to bed about the three versions of this movement.
There is often talk about the 7s26A being a poor to mediocre time keeper that is not adjustable. The truth is that it can be adjusted to keep as good time as the B and C versions. After all they are the same movement.
Let's look at the three balance assemblies...

7s26A

This one has a fixed and nonadjustable stud. It also has a regulator that can only be adjusted by bending the regulator pin. Knocks and jars do not generally cause the hair spring to jump around and get hooked on anything. This is because the spring is held captive by the regulator bar/pin assembly. To make adjustments at the stud end, the spring has to be bent. To make adjustments at the regulator, the pin has to be bent slightly to allow the hairspring to slide in the space between it and the bar then bent again to close the gap so that the spring does not move back and forth. Often, new enthusiasts will try to regulate the watch and end up putting a nasty kink in the spring because it is not free to slide in the regulator. This is a pain for watchmakers and also time consuming at the factory.
Once these adjustments are made, the 7s26A can be just as accurate and consistent as the other two versions.

7s26B

Seiko update the 7s26A balance system with the Swiss like etachron stud and regulators. Both pieces have rounded rectangular heads so that they can be rotated. The stud can be rotated so that the spring shape can be modified without actually bending it. The regulator now has two pins that are parallel to one another and when the head is rotated, the pins open or close around the spring. Again no bending required. This setup cuts way down on assembly time at the factory and makes it a lot easier to get optimum performance from the movement.
Unfortunately, in the 7s26B model, the design of the balance assembly is flawed. With a new spring material and longer regulator pins; the spring is somewhat floppy and easily knocked out of place and often gets looped around the outside of the stud of the regulator itself. Thus the many complaints about the B version.

7s26C

The 7s26C looks to be identical to the 7s26B but there are some real differences. Firstly, Seiko shortened up the regulator pins while redesigning the whole balance assembly. This was done to correct the previous issues and also to rationalize inventory across the 7s, 4r and 6r calibres.

Balance assemblies will interchange between the A and B versions but the C version only fits in itself.

All three calibres can be made to run as accurately as one another. The looping hairspring issue with the B version leaves us with the A and C as the better choices.
From an adjustment point of view, the C version is probably the best overall.

Hopefully, this clears up some of the misinformation floating around on the forums :c017: for reading.
 

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AqualandKing & Special Member
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Peter Sir to me that’s just a Riveting and educational read.
I hope more members appreciate the Effort and time taken to post👏👏👏👍😜
 

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Discussion Starter · #4 ·
Thanks guys; I appreciate the recognition.
It really is more about helping newbees and occasional enthusiasts to learn the subtleties of Seikology :bigdigitalwis:
 

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Craftsman
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Nice write up Peter. Very informative!
 

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Thanks for putting this information together. I'm fairly new to watch collecting and found this very informative.
 

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Really interesting information Peter and nicely laid out :clap:
 

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Nicely presented, though I will note that I had the “looping hairspring” issue with a C movement and, over the years, I’ve seen quite a lot of complaints on the forums from others who have too. So I wouldn’t say that the C-type (does that make anyone else thing of Jaguars?) “solved” the problem, but rather that it “mitigated” it.


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Discussion Starter · #14 ·
Nicely presented, though I will note that I had the “looping hairspring” issue with a C movement and, over the years, I’ve seen quite a lot of complaints on the forums from others who have too. So I wouldn’t say that the C-type (does that make anyone else thing of Jaguars?) “solved” the problem, but rather that it “mitigated” it.


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This is true...'mitigated' is probably the better word :cool:
 

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Could you elaborate on the 7sC regulator pins being shortened, which portion of the adjustable regulator pin is actually shortened? Overall length, slot length or the stop/dog end?? Cheers 😃
 

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Discussion Starter · #16 · (Edited)
Could you elaborate on the 7sC regulator pins being shortened, which portion of the adjustable regulator pin is actually shortened? Overall length, slot length or the stop/dog end?? Cheers 😃
Dave, I don't remember who made this observation; could have been Spencer or Randall or one of the other Seiko technicians on the forums.
What I do remember is that they mentioned the bottom(open end) of the regulator pin block was shortened.

Now you've got me curious so I'll open up one of my 'B' versions for some in close macros to compare with the 7s26C picture above.

Until then, I guess this is all fake news :grin:
 

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It would be great if you could directly compare them, I have a suspicion that there isn't any difference between them - but happy to be proven wrong if it clears this up 😃😊
 

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Discussion Starter · #18 ·
It would be great if you could directly compare them, I have a suspicion that there isn't any difference between them - but happy to be proven wrong if it clears this up 😃😊
I'll do my best but I no longer have the watch with the 7s26C either :undecided:

It may be that folks who were complaining about the hopping spring on the 7s26B just gave up complaining when the 7s26C came out and did the same thing.

Once I get my hands on a 'B', I will know for sure.

Knowing will let us all sleep better :grin:
 

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Terrific information, thank you for taking the time to do this work!


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I've worked with A's and C's. I find no substantial differences in performance or ease of adjustment between the A's and C's. But what I do find is inconsistency in performance. Depending on the watch, I can adjust them to keep time with less than 2 seconds variability a day or others that can have up to 40 seconds of variability no matter what I do. Also, compared to the old 6009's of the 80's that had 17 jewels, the rotor on a pivot with no ball bearings or jewels, they would start at the slightest movement, could be worn right away without spinning, and stored up 40 hours of reserve after normal wearing for half a day. Most 7s26's that I've encountered can be worn all day with full activity and they barely store up 15 hours of reserve. The so called improvements as far as I am concerned are just bells and whistles, with no benefit in performance for the consumer. They don't make em like they used ta.
 
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