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My first repair : Seiko 7S26C Oscillating Weight Failure


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Howdy,

 

Well, this is my first effort of a watch repair. I have been fascinated with watches, clocks and all kinds of mechanical things since a young age. I decided at this time that working on watches would be a great hobby/interest to take up in my later years. I have already spent some time learning to refurbish and repair fishing reels in the last few years. So here is my first repair attempt.

 

Interest in tinkering watches started when I dropped my Seiko SKX009KD diver to the tile floor in the bathroom. Was not too good an idea to put a watch on there with a towel thrown over it, pulled the towel and down comes the watch, face down on the tile floor. Needless to say, I picked it up and took a look, nothing seen. Then I shake it and hear a rattle. Not too good!

 

So I did some research on the 7S26C movements. Read a lot of information and watched a lot of videos. Thanks to all that makes this information available. So I purchased a cheap watch tool kit from Amazon. I had other watches that needed batteries and some strap work anyway. I knew the kit would not be 'pro' grade, but it was a nice kit with all the basic tools needed.

Back to the rattle, I figured the Oscillating Weight (OW) had become separated from the bearing. So I used the case back wrench in the kit and opened the back, and sure enough that was the problem. I looked on-line for a replacement OW but could not find any except one on Ebay for $35! So I decided, what the heck, I'll try to repair this one. So, here is what I did being a little mechanically inclined but never at this small a scale, I performed the following:

1) remove case back.

2) examine the OW, it was dislodged/loose from the bearing.

3) remove center OW bearing from center post.

4) place OW on a small anvil, then use a small pin punch from the kit as to carefully work the metal around the OW's hole as to make the bearing hole smaller.

6) After enough working with the punch, I took a smooth round stone and gently kept working the ID of the OW hole until it just would friction fit to the surface of the OW bearing.

7) carefully press fit the bearing into the OW, I knew too much pressure would ruin the small bearing races and ball bearings.

8) finalized fitting of the bearing to the OW by applying a very small amount of red Locktite thread locker using the end of a pin as an 'oiler'.

9) I then let the OW set for a day to cure the Locktite

10) install OW per alignment instructions in the 7S26C technical guide. At this time I also wound the mainspring up 8 turns to check the power, it ran for about 40 hours.

11) did not have any watch oil, so I used a very small amount of some 10W synthetic engine oil using a small pin as the oiler to lubricate the OW bearing ONLY.

It appears to be a successful repair for now, watch been running great and keeping good time for about 2 months. I'm sure something else might have gotten damaged during the fall, especially the balance assembly, but then again the watch is working fine for now. I might use this particular watch to dive deeper into the 7S26 movement at a later time. Kind of happy for now. Got 2 other watches running with new batteries, fitted some straps and having fun with my new hobby. Look forward to learning some more. Now to find a 'bag o watches at a flea market and get busy. I know I'm going to need more and quality tools down the road, that's OK with me.

Cheers,

Chip

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welcome to the forum!   some automatic watch main spring can be wound by the crown also.  this means you can take the counter weight out and wear the watch - or don't buy automatic watches -go-  to quarts watches.   as a hobby,  you could build a " automatic watch winder"  for less than $700 ?  in any event,  enjoy the forum and; Gods speed !  vin

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 Outstanding .You just took a practical look at it, rubbed your brain cells together and came up with a plan. I use synthetic motor oil as well. It is perhaps "improper"but it does work.I often wonder if "watch oil"isn't just mobil 1.

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Thanks all for the comments.

I have a question though. So this 7S26 movement is very popular, so can someone tell me why it' s hard to find a OW for it? Seems there should be a lot of those available. Maybe Seiko does not make many spare parts available? As mentioned I can buy a brand new movement for about $48, or a new OW on ebay for $35. To me it would be better to just buy a new movement would it not?

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It costs money to stock things.Its like fixing a car. You could by the whole vehicle for thirty grand, but one piece at a time it would cost you double.So now the choice is yours, pay 35 bucks for a weight to stick on an old movement or buy a whole new one for 48 ? personally I would spring for the extra dozen bucks...OR since you have already made an effective repair, use it as is.

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23 hours ago, yankeedog said:

It costs money to stock things.Its like fixing a car. You could by the whole vehicle for thirty grand, but one piece at a time it would cost you double.So now the choice is yours, pay 35 bucks for a weight to stick on an old movement or buy a whole new one for 48 ? personally I would spring for the extra dozen bucks...OR since you have already made an effective repair, use it as is.

I understand the cost thing and it makes sense. As mentioned since it was dropped, of course it would be logical to buy a new movement for the extra bucks than spent the money on a OW.  I'm sure something else might have gotten damaged. I will use this one to learn on once it is no longer working properly.  Like you said, It's fixed for now so I'll see how long it last.

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Quote

11) did not have any watch oil, so I used a very small amount of some 10W synthetic engine oil using a small pin as the oiler to lubricate the OW bearing ONLY.

The worst oiling sin I will confess to, was nicking some engine oil from the dipstick to lubricate an old alarm clock. It worked fine, but obviously I wouldn't recommend this as a normal course of action, and certainly not if you were doing this for a paying customer.

As to what secret sauce is in genuine watch and clock oil, short of sending some to you local chemical wizard to be analyzed I'm not sure how you would ever know.

What I do know is that in the not so distant past, they used sperm whale oil for this application, and since many ancient timepieces still survive, I don't think the exact oil is invariably critical.

Modern synthetic watch and clock oils are much more rigidly refined and have specifically selected temperature, viscosity and aging profiles, but you will get away with motor oil at a pinch.

Some lubricant, in the correct places, and in the correct amounts, and cleaned off and replaced at regular service intervals is almost invariably better than no lubricant at all.

Edited by AndyHull
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Sperm whale oil was once a key component of automatic transmission fluid.We almost wiped out a whole species because we were to lazy to step on a clutch. ATF had to be reformulated..to replace whale oil.draw your own conclusions

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On 3/21/2019 at 4:15 PM, George19 said:

I have a question though. So this 7S26 movement is very popular, so can someone tell me why it' s hard to find a OW for it? Seems there should be a lot of those available. Maybe Seiko does not make many spare parts available? As mentioned I can buy a brand new movement for about $48, or a new OW on ebay for $35. To me it would be better to just buy a new movement would it not?

Actually Seiko parts are among the easier to find. And if someone needs a 7S26 trivial part can always ask here, myself and (I guess) others are willing to donate for the purpose of education. And yes learning and equipping to to fix things oneself can cost more than replacing, any hobby has a cost.

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  • 11 months later...

I just got a new 7s26 movement from China and tried to replace the oscillating weight because of the ball bearing failure (check the video for the noise). But unfortunately, this other oscillating weight is doing the same noise. I screwed down the screw as much as I could, but still no luck :(.  Here is a video

Are all 7s26's doing the same noise?
I put a small amount of silicone grease on the ball bearing (rotor) of the OW, and it's making significantly less noise.

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1 hour ago, Genti said:

I just got a new 7s26 movement from China and tried to replace the oscillating weight because of the ball bearing failure (check the video for the noise). But unfortunately, this other oscillating weight is doing the same noise. I screwed down the screw as much as I could, but still no luck :(.  Here is a video

Are all 7s26's doing the same noise?
I put a small amount of silicone grease on the ball bearing (rotor) of the OW, and it's making significantly less noise.

You should see about the right lube in relevent datasheet.

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45 minutes ago, Genti said:

@Nucejoe Where can I find this relevant datasheet? I just put a very small amount of silicone grease tbh, I don't think that will cause any damage, will it?

If a link to the datasheet is already not provided on this forum, I am sure our helpful member watchweasol will soon post the link here.

 

 

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1 hour ago, Genti said:

@Nucejoe Where can I find this relevant datasheet? I just put a very small amount of silicone grease tbh, I don't think that will cause any damage, will it?

Do not use anything but a minuscule amount of fine oil for thr rotor bearing, as that will hinder its working.

The service sheet is attached to almost any 7S26 discussion, and here again. You can always use the search function to get answers without waiting for other to reply.7S26C.pdf

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11 minutes ago, Genti said:

@jdm in that case, how do you suggest I should clean the silicone grease from the rotor bearing? As I don't have any idea.

Yes, remove the rotor and soak it in alcohol.

Edited by jdm
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Just now, Genti said:

@jdm I know I have asked too many time but should I just leave the noise of the rotor be like that after I clean it?

Read above about lubricating the ball bearing.

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1 minute ago, jdm said:

Read above about lubricating the ball bearing.

but lubricating with just fine oil didn't make the noise less. Maybe because silicone grease is thicker, therefore it did.

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18 minutes ago, Genti said:

but lubricating with just fine oil didn't make the noise less. Maybe because silicone grease is thicker, therefore it did.

It perfectly normal for some Seiko rotors to make a little noise, but apparently some owners are much bothered by that, as the issue keep being posted on forums. You can of course apply whatever you want to your watch, then if does not auto wind as per specifications you will know why is that.

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5 minutes ago, jdm said:

It perfectly normal for some Seiko rotors to make a little noise, but apparently some owners are much bothered by that, as the issue keep being posted on forums. You can of course apply whatever you want to your watch, then if does not auto wind as per specifications you will know why is that.

I don't know how you define little noise. But if you look at the video I don't think that it is little noise. :(

When it comes to winding, it does wind with silicone grease in it. I thought that you mean to not use silicone grease because it might end up in the actual movement.

Edited by Genti
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5 minutes ago, Genti said:

I don't know how you define little noise. But if you look at the video I don't think that it is little noise. :(

When it comes to winding, it does wind with silicone grease in it. I thought that you mean to not use silicone grease because it might end up in the actual movement.

I define little noise based on having handled hundreds of these watches. Some are totally silent, some are slightly audible, especially when the thick diver caseback is removed as in you video. Clearly there are different manufacturing tolerances, if we perhaps the China made ones are the worse. Incidentally Seiko never officially acknowledged to have movement manufacturing in China.

If you want to know how well it auto winds with grease in the bearing check how many hours of running you get from the end of a normal day on the wrist. If you get the standard 40 then that's another prove of the exceptional efficiency of the system.

 

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Below a video about the importance and testing of the rotor bearing free spinning. A Seiko bearing in good state behaves very similarly. Lubrication decreases the efficiency of the bearing but makes it to last longer. 

 

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11 hours ago, jdm said:

Below a video about the importance and testing of the rotor bearing free spinning. A Seiko bearing in good state behaves very similarly. Lubrication decreases the efficiency of the bearing but makes it to last longer. 

 

Mine behaves just like the bad one. Stops after 10secs or less. New oscillating weight for 7s26c are very expensive at 32$ on ebay. :(

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