[time-nuts] Adjusting accuracy of a Casio G-Shock watch

Jim Palfreyman jim77742 at gmail.com
Wed Dec 15 07:15:17 UTC 2010


Bill,

Indeed undoing the four screws is all that's needed. However on some
models those screws are covered by various plastic bits which are
quite confusing to remove. (Unless you are a gshock-nut!)

Jim

On Wednesday, 15 December 2010, Bill Hawkins <bill at iaxs.net> wrote:
> Jim,
>
> I have such a watch, purchased in Singapore in Oct 2009. It is
> solar, but it has no radio connection. It is water-resistant
> to 20 atmospheres (bar). I don't wear it, but I keep it by a
> southern window.
>
> The back cover appears to be held on by four screws. I've not
> tried to open it. It's off by two hours and 91 seconds, over
> a year. It's possible that I didn't make the final time zone
> adjustment when I got back to Minnesota.
>
> What was the problem with getting the back off?
>
> Bill Hawkins
>
>
> -----Original Message-----
> From: Jim Palfreyman
> Sent: Tuesday, December 14, 2010 10:17 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Adjusting accuracy of a Casio G-Shock watch
>
> Fellow time-nuts.
>
> Over in another part of the internet is a group of people who love their
> Casio G-Shock watches. These digital watches have been around for decades
> and are built very well.
>
> The one I own is an "atomic" and solar model (i.e. no battery replacement).
> However being in Tasmania, I cannot receive the low frequency time signals.
> When I first received the watch it's accuracy was excellent. Under 10
> seconds a year. I even posted on here about it. Since then though it has
> drifted somewhat.
>
> After a ton of internet searching on how to open the case and how to adjust
> these watches (this is non trivial as the models are all very different and
> no instructions existed for this model - the GW-810D) I have finally cracked
> it.
>
> Interestingly, the module has a pad that gives off a stepped square wave at
> 32768/48 Hz. So with well calibrated equipment (which we all have of course)
> it is trivial to adjust the trimmer to put the watch back to decent
> accuracy. Using the smallest adjustment of the trimmer that I could muster I
> could get it down to about 0.5 in 10^6 or 1 second in around 20 days. Not as
> good as when I got it - but I was probably just lucky.
>
> Over in mygshock.com they struggle with this sort of timing stuff - whereas
> my big deal was opening the case!
>
> Just posting in this in case anyone here is interesting in adjusting their
> G-Shock.
>
> Jim
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