Possible power reserve issues on miyota 9015
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  1. #1
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    Possible power reserve issues on miyota 9015

    Last week I received a Phoibos Eagle Ray, which has a miyota 9015 movement. It appears to have some power reserve issues. I first noticed it within the first day of having it. I had given it a few hand cranks to get it going and then after sitting around relaxing, I looked down and noticed it had stopped. No big deal I thought, I just only given it a few cranks and hadn't really moved. On Saturday someone asked me what time it was and I was about 45 minutes behind, unbeknownst to me. I wasn't sure if this was a power issues or if it was losing time that badly, because I had never noticed it not running. I did a time study on it and over the course of two days it lost about 3 seconds. During this time I had made a point of winding it a few times throughout each day to make sure it kept going as I wasn't wearing it the entire time. I had worn it from about yesterday afternoon at 4:00 PM until about 10:00 PM.

    It was still running this morning. I gave it a solid 20+ cranks until I could feel the tiny bit of periodic spring telling me it was fully wound. I work a desk job, but I still move about a good bit. I've never had an issue with any of my other automatics stopping, including my Orient sun and moon which doesn't have any hand wind option. At about 3:15 I looked down and noticed that it had once again stopped, and had been for about 40 minutes. When I took it off I gave it a few side to side motions to get it going again followed by 40+ hand cranks. It's clear that I'm going to have to do a full time study to see how long it's lasting, but I have to imagine something is wrong. I have never had an auto stop working while on my wrist, especially after I had been wearing it for hours and had given it some cranks not even 8 hours earlier. The only possible thing I could think of is that because the movement is unidirectional that it won't charge as easy as some of my others, but that still doesn't explain the loss of power when I had hand wound it. Any thoughts on the issue before I prep to go down the warranty path? I have continued to do time studies and it has continued to keep time without issue, it's just had multiple occurrences of unexplained stops at this point. I don't have a winder and am finally debating getting one, but that still doesn't explain why it would lose all power on my wrist after all of the hand winding.

  2. #2
    Member fastfras's Avatar
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    Re: Possible power reserve issues on miyota 9015

    Your mainspring may be damaged, I had a similar issue with an automatic a few weeks ago and found the M/S needed replacement.
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    Re: Possible power reserve issues on miyota 9015

    IIRC, these require 40 full rotations of the crown to get full PR from dead.

    Also, the Miyota has a unidirectional winding rotor, so it will not wind as efficiently on wrist as a bi-directional like anything from Seiko, Orient, most ETAs (except the 775x chrono's), etc.
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    Re: Possible power reserve issues on miyota 9015

    They're actually very efficient auto-winders, in my observation, having made a few thousand watches with the 9015.

    @Floataround - you need to do some troubleshooting. Hand-wind it to full power by turning the crown 40 full turns, and see how long it runs. If it runs more than 40 hours, odds are you just weren't moving around enough to keep it running.

    The defect rate on the 9015 is very low. But, those bad units we've found, almost always presented themselves soon after delivery.
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    Thanks all. I'm going to do a few documentied time studies before contacting phoibos.

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    Re: Possible power reserve issues on miyota 9015

    Quote Originally Posted by docvail View Post
    They're actually very efficient auto-winders, in my observation, having made a few thousand watches with the 9015.

    @Floataround - you need to do some troubleshooting. Hand-wind it to full power by turning the crown 40 full turns, and see how long it runs. If it runs more than 40 hours, odds are you just weren't moving around enough to keep it running.

    The defect rate on the 9015 is very low. But, those bad units we've found, almost always presented themselves soon after delivery.
    Efficient for a unidirectional, but when the rotor winds in both directions, you get winding with pretty much every movement of your wrist. Not so with unidirectional. If you're not very active, I could definitely see unidirectional winders running out of steam before bidirectional.
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    Re: Possible power reserve issues on miyota 9015

    Quote Originally Posted by MX793 View Post
    Efficient for a unidirectional, but when the rotor winds in both directions, you get winding with pretty much every movement of your wrist. Not so with unidirectional. If you're not very active, I could definitely see unidirectional winders running out of steam before bidirectional.
    I recall an article that compared the two methods and the results were absolutely not that clear on this issue. The drawback with bidirectional winding is that the wheel that switches from one direction to the other creates a dead zone when switching. When the rotor changes direction, it takes some rotor angle to move the wheel over to engage on the other side. During this dead zone, the watch doesn't wind at all. Unidirectional winding has no such dead zone, and in the free direction the rotor also swings further up, possibly building up more potential energy for the next swing in the productive direction. So both systems have their advantages, and it's not that simple to say that one is more efficient than the other.

    Seiko's magic lever is a bidirectional winding mechanism that comes without the dead zone for switching directions, by the way, which is pretty neat.

  9. #8
    Member docvail's Avatar
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    Re: Possible power reserve issues on miyota 9015

    Quote Originally Posted by MX793 View Post
    Efficient for a unidirectional, but when the rotor winds in both directions, you get winding with pretty much every movement of your wrist. Not so with unidirectional. If you're not very active, I could definitely see unidirectional winders running out of steam before bidirectional.
    Trust me, it's very efficient, in absolute terms, even compared to a bi-directional winder, not just for a uni-directional winder.

    It's a fallacy to assume bi-directional winders are more efficient. Only an empirical test can prove something like that. We've done empirical tests comparing it to bi-directional winders, and the 9015 won, easily.

    Bi-direcitonal winders have resistance in both directions. The 9015 has little to no resistance in the non-winding direction, and only light resistance in the winding direction. The auto-winding mechanism on the 9015 is extremely efficient at using body motion to power the watch.

    As a side benefit, it's thinner, and there's less wear-and-tear with the unidirectional winding.

    We've made over 3,000 watches with the 9015, and about 2,500 with bi-directional winders, both Japanese and Swiss, so we've had a lot of experience with reports of possible PR issues. The reports from the bi-directional winders far outnumber the 9015.

    In almost every case, the troubleshooting revealed the cause to be that the watch owner simply wasn't moving around enough to keep the watch wound, nor were they giving the watch enough hand-winding to keep it going in lieu of physical motion. But, the salient point here is this - the guys who aren't moving around very much are getting more power out of their 9015's than the guys with the bi-directional winders, even at their low activity level.

    Basic troubleshooting:

    1. Hand-wind it to full power - see how long it runs. If it runs for ~40 hours, repeat in as many positions as necessary to convince yourself it's not stopping due to some positional variance (it can happen).

    2. If the watch passes the above test, then it's not a PR issue, and the only thing left to rule out is some fault in the auto-winding mechanism. Shake the watch back and forth in your hand, dial up, for about two minutes straight. That should be more than enough to keep it running 6-8 hours, at a minimum. If it stops prematurely, then have the manufacturer or a watchmaker take a look at it. A watchmaker can put it on an auto winder and tell if there's something wrong within 24-48 hours.
    ffritz and NC_Hager626 like this.
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  10. #9
    Member Nokie's Avatar
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    Re: Possible power reserve issues on miyota 9015

    You received some serious professional advice here.

    Good luck.
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  11. #10
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    Re: Possible power reserve issues on miyota 9015

    It certainly sounds like you may have an issue with it but you’ll only know for sure once you’ve put it to the test.

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