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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
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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
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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
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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.
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.
