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Seiko 7S26A Complete Service Walkthrough

Lawson
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jdm Distinguished Member

jdm

Posted
Posted

OK just looked at the timeograph reading and not much amiss wondering if it,s just the mainspring is not winding fully.

 

How the MS could not wind fully after more than 10 turns at the barrell? Now it has stopped again with a full charge.

 

I went back to the other one which has an even smaller amplitude, and is still going. It kind of works albeit with large sweeps in rate within one timegrapher screen interval. I'm sure it's not worth to be cased anyway.

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Lawson
Lawson

Seiko 7S26A Complete Service   Background   I have a good friend, a brother in Christ Jesus, who I've known for many years.  He knows I've embarked on retraining myself for a new career in Watchma

Lawson
Lawson

Assembly   This is a very easy watch to re-assemble.  In fact I'd recommend the 7S26A to be the first Japanese Movement to practice on, because it's so beautifully and logically laid out.  The only

Geo
Geo

That's a well put together post and great illustrations. Anyone about to embark on servicing or repairing one of these will find it very helpful.

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bobm12 Distinguished Member

bobm12

Posted
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Hi Scotty,

 

Sorry, we were waiting for your input as you promised in your last post. In my mind, the problem you have is a shorted hairspring. It may be a number of reasons. Oil in the coils, coils touching, etc. Since you already demagnetized it then I would immerse it in lighter fluid and check again. Of course, before anything I will inspect that all coils are perfectly concentric without touching. If touching you will have to "repair" it. Mark has a good series of videos of how to go about it.

 

Cheers,

 

Bob

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bobm12 Distinguished Member

bobm12

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Hi jdm,

 

As CB said, in Seikos, amplitude is not too great. So, your primary goal is to make them work continuously in all positions. Remember, if running fast, most likely it is a shorted hairspring. In your case, I suspect the pivots. They could be rusted, bent or broken. This may be an issue detected when the watch runs in one position but doesn't in another, usually an oposite. Also, check for fork jewels misaligned, worn, and/or broken...or similar problem in the balance/impulse jewel. Those are critical areas for the watch to work properly given that the rest is OK.

 

Hopefully, it is just a little overlooked detail. It sometimes happens that we are so focused on the Gremlins that a little thing may just pass us by. Happens all the time. Remember magnetism is one of those we overlook...and some demagnetizers (read cheap) might add the magnetism.

 

Cheers,

 

Bob

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SCOTTY Watch Enthusiast

SCOTTY

Posted
Posted

Hi Bob,

 

Thanks for replying. I haven't got to it yet but remember this is a 7s36C and the complete balance assembly is the only thing I left untouched. I dismantled everything else, along with soaking, cleaning & oiling where necessary. Since I didn't

oil the balance assembly either I don't see where oil on the h.s. could have happened. I don't think I damaged it but I'll keep checking. How could the h.s. have shortened? When I get to it I'll try soaking the hairspring too. Again, this is my 1st

overhaul & I thought it would be a good idea to step away for a bit. I do have a question. Is it possible for it to continually run with the roller jewel not seated correctly? Could that be the problem? I'm thinkin no. Thanks again Bob!

 

Cheers,

Scotty

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bobm12 Distinguished Member

bobm12

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Difficult but I suppose that's not impossible if something is bent or out of shape. I've never had that problem myself. Maybe when manipulating the balance assembly the hairspring got out of shape or some debris/oil drop fell on the hairspring proper, shorting it. (Sorry, not shortening I meant shorting). Just look for out of shape and/or touching coils.

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SCOTTY Watch Enthusiast

SCOTTY

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Here are some shots of the balance assembly in the mainplate. I used a blower to spin it & it seems to oscillate smooth coming to a slow stop. I couldn't see any sticking. I also looked @ another 7s36

& they look the same (Oscillating & @ a dead stop). I guess It's my inexperience & untrained eye. If anyone sees anything in these pics please let me know. Thanks!

 

Scotty

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Blacklab Distinguished Member

Blacklab

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Jdm, avoid using alcohol particularly around the balance & pallet as it has a tendency to dissolve the shellac holding the jewels in place, as Bob rightly states lighter fluid is the safe option. I normally get amp readings of 240-270 on Seiko 6xxx & 7xxx series.

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jdm Distinguished Member

jdm

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Jdm, avoid using alcohol particularly around the balance & pallet as it has a tendency to dissolve the shellac holding the jewels in place, as Bob rightly states lighter fluid is the safe option. I normally get amp readings of 240-270 on Seiko 6xxx & 7xxx series.

 

Thanks. Being aware of that, I didn't place pallet fork in alcohol. 

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Geo Distinguished Member

Geo

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I'm having trouble finalizing a post with pics on this topic.  HELP !!   :pulling-hair-out:

If you mean when yo are trying to attach a picture when replying.

(1) Click on the "More Reply Options" at the bottom right hand side.

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(2) Click on "Chose File" button and a drop down menu will appear.

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(3) Click on "Photo Library"

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(4) Select image.

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(5) Click on "Attach This File"

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(6) Click on "Add To Post"

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(7) Click on "Preview Post"

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(8) The picture should appear.

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(9) Finally click "Add Reply" and jobs done!

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SCOTTY Watch Enthusiast

SCOTTY

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Posted (edited)

Hope this works..........  I dont believe it !!  I thought I did this before. Must have missed something. Thanks Geo. Anyway, if anyone notices something wrong with the h.s. let me know. Thanks !

Scotty

 

 

 

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Geo Distinguished Member

Geo

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It's way off centre.

It might be magnetism or oil contamination causing it, but the end stud and regulator stud look very far out in their locations and could be pulling the spring over to that side. This is only a suggestion, so I hope someone else pitches in with other ideas.

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SCOTTY Watch Enthusiast

SCOTTY

Posted
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It's way off centre.

It might be magnetism or oil contamination causing it, but the end stud and regulator stud look very far out in their locations and could be pulling the spring over to that side. This is only a suggestion, so I hope someone else pitches in with other ideas.

Thanks. I understand. 

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clockboy Distinguished Member

clockboy

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Agree with the above the hairspring is the issue. It the pics are showing correct it is out of centre hence the low amplitude. I would first give it a good soak in "Horosove" or "One dip" 

       

As a side issue regarding amplitude. I have never achieved a really good amplitude with any of the Seiko,s I have serviced. It appears the pro repairers always seem to fit a new mainspring when servicing them & I wonder if this is the reason.

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jdm Distinguished Member

jdm

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Thanks. I understand. 

 

Stud and regulator appears to be in the normal position as they are in new movements delivered from factory. Remove balance, turn ir over and a take a pic with camera directly vertical over it. For better results, you can set the camera to maximum resolution, then cropthe  picture to center only. Also, leaving the balance cock on the table, pull the staff out if it, let it be near the jewel and check where it want to stay naturally, if on center or not.

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bobm12 Distinguished Member

bobm12

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Hi jdm,

 

Can you clarify the last sentence. I'm not sure what you mean - or the procedure -- but I'm really interested. Thank you in advance.

 

PS. if you have some way of illustrating it, it will be perfect!

 

Cheers,

 

Bob

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jdm Distinguished Member

jdm

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Can you clarify the last sentence. I'm not sure what you mean - or the procedure -- but I'm really interested. Thank you in advance.

 

PS. if you have some way of illustrating it, it will be perfect!

 

This is an hint I got a from a watchmaker which is quite active on various forums. The idea is that an hairspring which is not perfectly concentric will not naturally bring the balance staff to the jewel hole. I found that to be true. Just place cock or bridge upside down on the mat and check where the staff tends to go when lifted a tiny bit and let go. 

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