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Discussion Starter #1
Hi All
I've just been lucky today and managed to pick up a 6146-8000 hi beat GS but it needs a new mainspring. Does anyone have or know of a source for part number 201615? I understand that the mainspring is set inside the barrel so that both have to be replaced.

If a complete part is not available, is it possible to open the barrel and substitute a different mainspring?

I'm also after a new crystal, 310T08AN.

Thanks,

Gordo
 

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If you want to see your watch run before you become an old man looking for that part , use the barrel and spring out a 6309 movement.
 

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If you want to see your watch run before you become an old man looking for that part , use the barrel and spring out a 6309 movement.
That's a similar idea to the Japanese blogger - he used a 6138 mainspring #401616
 

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Discussion Starter #6
Thanks all for the replies and to Grammar for the crystal that is now making its way to me.

I tried a translation of the blog pages and though a bit garbled, there was some interesting information. Mmounce, is the 6309 barrel and arbor a straight drop in replacement? Will the movement still run at 36000 and what about the power reserve?

Thanks again,

Gordo
 

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Hi-beat movements generally have stronger mainsprings - so the reserve may be less.
You could try measuring your original spring and checking against a standard one, to see if its thicker.
 

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Here are some thoughts I'd saved on the dilemma of the hi-beat 61 barrel assemblies, specifically the 6159.

The barrel cover is on the upper side, and it is definitely burnished into place, meaning one cannot push it off with the arbor without potentially destroying the cover, drum, or both. The mainspring is much thicker than the standard 61xx springs, so there are fewer coils inside the barrel- it has about 5.5 turns to a full wind vs. 7.5 turns on a standard 61 mainspring. Otherwise, the barrel and arbor dimensions (at least from the outside) are identical to a 61xx or 63xx barrel (205613) (heights, diameters, number and size of teeth, etc.).
I installed one such barrel to experiment, and the watch ran fine with it. Detailed timing analysis showed a predictable drop in amplitude due to the weaker spring, but I think that if you had a broken mainspring or a barrel missing a tooth or overly worn, this might be a solution until a correct barrel assembly came along. Your positional errors might increase a little due to the lower amplitude, but the higher beat should mask a lot of that. The automatic winding efficiency would be a little too high given the heavier oscillating weight of the hi-beat caliber, but that shouldn't cause anything terrible, especially if the watch isn't a daily-wearer. You would also obtain a longer power reserve, theoretically (depends on how low the state of wind can get before it no longer is enough to power the balance- I did not check this). I counted the teeth on the barrel and center wheel, and in theory 7.5 turns of a standard 61xx/63xx mainspring should give no more than 52.5 hours of run-time, while the 5.5 turns of a 6159 spring should give no more than 38.5 hours. It will necessarily be a little less than this in practice.
I'd like to experiment further, but even damaged barrel assemblies are thin on the ground. While a substitute of the same dimensions to the original mainspring may be obtainable, the problem is getting the barrel open, and then also getting it closed. They aren't designed for this, and most available methods to open and close seem like a compromise to me, unless one is willing and able to make replacement covers and/or drums. I guess you could use a 6309 barrel drum and cover, though.
 

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Discussion Starter #10
Wow, what a fantastic and extremely useful lot of replies. The depth of knowledge on the forum is always amazing. So it sounds like the best solution is going to be a 61 or 63 barrel and arbor with either a 61 or 63 mainspring or perhaps the mainspring that Cousins lists for the 6146. Hopefully that spring is heavier so the amplitude will be closer to original spec.

On a side note, this watch is one of those classic 'barn finds'. It was purchased for the the princely sum of $30 Australian from an antique centre in Toowoomba. Amazing where these things turn up. I'll post a picture of the watch later today.

Thank you again to everyone for the help and advice.

Kind Regards,

Gordo
 

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Gee whiz, I wish I had a Toowoomba over here. Congratulations on your find, and please save the next one for me!
The 6106 and 6309 (and many related calibers, such as 6105, 6119, 6349, etc) all take the same mainspring and barrel, so when I referred to the 61 series parts, it is all the same. Sorry for any confusion.
 

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Discussion Starter #12
This the watch in question. Just a couple of quick and dirty shots I took at work today. Sad though this sounds, I actually wore it all weekend, even though not running. Thrilled to have added my first Grand Seiko to the collection.







Now the question is whether to polish the case or leave well enough alone.
 

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Clean only, please do not polish! It can never be "un-polished", nor finished *exactly* the same way that Seiko did it 40 years ago. You'd be destroying a historical account of their abilities at that time, on a rare peice.
 

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Discussion Starter #14
Hi Noah
Yes that's pretty much what I was thinking. Generally with any of my vintage pieces I try to do the minimum amount of re-finishing. With this one I think just a good ultra-sonic clean and a fresh crystal and case back gasket will do the job. Maybe down the road a bit a steel GS buckle would be a nice addition.
 

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Hi Noah
Yes that's pretty much what I was thinking. Generally with any of my vintage pieces I try to do the minimum amount of re-finishing. With this one I think just a good ultra-sonic clean and a fresh crystal and case back gasket will do the job. Maybe down the road a bit a steel GS buckle would be a nice addition.
Agreed !
 

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Hi
cousins list a generic mainspring for that model in these dimensions, 1.05 x .15 x 340 x 10.5
I've no idea on the size details of the original but the cousins one might be closer than the 6309 etc.
Borels list two barrels for that model with one being described as complete and one described as sealed with different part numbers, Maybe the one listed as complete might have a removable lid ? (complete conjecture)

seikola
 

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I read a blog where the 7s26 mainspring was measured as 0.92mm x 0.1mm. 4R15/6 is the same size but wound differently, plus the arbor end is formed to a smaller diameter.
 

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Discussion Starter #18
The spring I have on order from Cousins sounds like the one your talking about Seikola. I also have a NOS 6309 barrel and arbor coming from Stefan. My hope is that the generic spring will fit the 6309 arbor. I guess if not then I'll have to order a 6309 spring.

7s26, could you post a link to the listing at Borels?

Thanks,

Gordo
 

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It was Seikola who mentioned the Cousins link :)
 
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