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How to remove an old balance wheel-hairspring on the 7s26 movement and replace it with a new one.

Roger2020

By Roger2020
in Watch Repairs Help & Advice

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Roger2020 New Member

Roger2020

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Hello and thank you for your forum. I have a Seiko 5 with a 7s26 movement. On a timegrapher machine it shows very low amplitude and ++++ rate. I think there is a problem with the balance wheel-hairspring. I demagnetized the  assembly to no avail. I bought a balance wheel-hairspring replacement but I cannot remove the old balance wheel-hairspring from the balance cock. There is no screw on the spring stud to secure the hairspring to the balance cock. Your help is very much appreciated. 

 

Regards,

Dariush.

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wudce Watch Enthusiast

wudce

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Posted (edited)

It is just press on. Like Mark I use a pair of hand lifting tools. You will also have to make sure you set it in beat. Mark has a video showing how to do this for some reason I can't link it here. Just google How To Align The Hairspring to set the watch in beat Watch repair techniques.

Edited by wudce
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Roger2020 New Member

Roger2020

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Thank you for your reply. I have seen Mark's video on how to set a watch in beat. The balance assembly of my watch is different and Mark address a different issue. My problem is how to remove the old balance-hairspring and install a new one. Please see the photos. As you can see there is no screw on the hairspring stud.

213321705_7s26balanceassembly4.jpg.7308b5ef5501561293ba07b9b1a82b04.jpg

 

1922813090_7s26balanceassembly8.jpg.8b1e7e44d5eead1f80bffb1569a837a2.jpg

7s26 new ballance-hairspring.jpg

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Marc Distinguished Member

Marc

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Reading what the OP has written it seems that the question is about removing the balance/hair spring complete from the balance cock, not the hair spring from the balance.

This is an Etachron type system in which the stud is a friction fit between the two prongs of the stud carrier fork. I have to confess that as yet I haven't played with one of these as most of watches I work on pre-date Etachron, however I believe that you just push the stud out of the fork, carefully so as not to damage anything.

Obviously your new balance complete has to have the Etachron style stud, and again, I believe that installing it is simply a matter of carefully pushing it into the carrier fork. I trust that someone with actual experience will correct me if this is wrong.

Once installed the position of the balance relative to the pivot hole, and the hair spring geometry (concentricity) are adjusted by moving the stud closer to or further away from the pivot jewel within the forks, and by rotating the stud by the flats on its top surface.

Adjustment of the curb pin clearance is also achieved by rotating the pin on the regulator arm.

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Nucejoe Distinguished Member

Nucejoe

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I insert tweezers into the space between stud and frok, wiggle to push the stud out, some easily come out, some might not want to.

You can make fork out of an old screwdriver to splinter over one prong of the stud fork and push the stud out, this reduces the risk of stud flying out.

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JohnR725 Distinguished Member

JohnR725

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10 hours ago, Roger2020 said:

I think there is a problem with the balance wheel-hairspring.

unfortunately in watch repair balance completes for every single watch you work on is not always available. It would be really good to develop the skills to figure out why your balance was having a problem.. Initially at least the pictures I can see it doesn't appear to be much seriously wrong though it does look like a minor bend in the hairspring. This is where really good pictures of the balance in the watch would've been helpful.

then when working with the etachron system tools are available.

etachron tools.JPG

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Nucejoe Distinguished Member

Nucejoe

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4 hours ago, Nucejoe said:

I insert tweezers into the space between stud and frok, wiggle to push the stud out, some easily come out, some might not want to.

You can make fork out of an old screwdriver to splinter over one prong of the stud fork and push the stud out, this reduces the risk of stud flying out.

So, I have copied bergeon 30081 EETC tool, made one out of a broken circuit test light. 

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spectre6000 Distinguished Member

spectre6000

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NueceJoe got it. The stud is friction fit in a fork with a bit of a detent. It pops out the side. Not always easily. Be careful, because it can try to pivot instead of slide, and the hairspring gets borked (guess how I know). It may vary from watch to watch, but on the one I worked on (broke), it was extremely stiff and took an uncomfortable amount of force to get it out.

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wudce Watch Enthusiast

wudce

Posted
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4 hours ago, JohnR725 said:

unfortunately in watch repair balance completes for every single watch you work on is not always available. It would be really good to develop the skills to figure out why your balance was having a problem.. Initially at least the pictures I can see it doesn't appear to be much seriously wrong though it does look like a minor bend in the hairspring. This is where really good pictures of the balance in the watch would've been helpful.

then when working with the etachron system tools are available.

etachron tools.JPG

Can't have too many tools I guess.

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Roger2020 New Member

Roger2020

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2 hours ago, wudce said:

Can't have too many tools I guess.

Thank you guys for all your help and suggestions. It seems that there is a consensus in how to deal with this problem. I will do the way it is described and let you all know about the result.

 

Regards.

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