Power Reserve Issues

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Howdy, folks. It's been a while since I posted, but it looks like I might have an issue and need your guidance.

I can't seem to get anywhere near the 48-ish claimed hours of power reserve out of my SMP300. The best I can hope for seems to be about 24-36 hours. Basically, I can't allow the watch to go from a Friday night to Sunday morning without having to reset and rewind.

In a previous post, I asked about how much we needed to wear such a watch - in other words how many hours per day - to ensure the power reserve was where it needed to be, and my fear is ovewinding the watch manually to get it going for long enough to last the stated amount of time.

Other than that issue, the watch has performed flawlessly since I got it back from a factory service just over a year ago, at only about +0.5 seconds/day. Truly impressive, but the power reserve thing irks me because I can't take a day without wearing it for fear of having to reset. It's a bit of an inconvenience.

Can someone shed some light on this?
 
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It doesn't sound like you are really testing the power reserve. Did you try winding it manually? You can't overwind it. Turn the crown 50 times and don't wear it. Then tell us how long it runs before stopping.

If it runs for 48 hours or so after a full manual winding, then that means the power reserve is fine. There could be something wrong with the auto-winding mechanism, but we don't know that yet.