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A fellow HeQ forum member asked me to give some follow up information regarding the somewhat unusual Casio LCD watch I obtained with a 4 mHz (actually Casio says 4,194,304 Hz) movement.

The watch was purchased from a seller in Japan. For a Casio LCD it was fairly expensive. For a 4 mHz movement, it was just somewhat expensive.





A close up of the face reveals the 4 mHz designation.





The back of the watch gives information on the calibre and model number. Calibre 75, Model number H103G.





Removing the back unveils the large lithium battery.





However, removing the battery reveals very little about the movement.





The watch was purchased in May, 2007 so I have had some time to determine its time keeping ability. It performs marginally better than a typical quartz watch. It gains about 0.3 sec/day, but seems to have very good temperature stability. I noticed very little change in the rate when going from a controlled temperature of 84 F to an uncontrolled temperature which varied from 68 to 74 F. The watch's gain went from +0.3 sec/day to +0.32 sec/day.

I have not determined how or if the watch movement can be regulated. No one at Casio seems to know much about this particular movement.

I have obtained some documentation (from Casio Japan) in English on how to set the watch and other documentation in Japanese on how to set the watch and perhaps perform other adjustments. The documentation indicates that other watches with this movement have accuracies in the range of 10-15 sec/yr (I am just guessing here). They could mean 10-15 sec/month which is more in line with my measurements. In that case I have a relatively normal accuracy quartz movement that is fairly immune to temperature changes.

Other than the 4 mHz movement, the watch is pretty standard Casio issue and would not qualify for HeQ status. The 4 mHz movement sets this watch apart as one of only a few such movements. I don't know if Casio produced other watches with this movement. The documentation may indicate that at least 3 other models were produced. I have heard of (but not seen) an all stainless version of the H103. The "G" probably indicates a gold plated version.

Since the time keeping accuracy of the watch is not anything to get excited about, I wonder why Casio would make a movement with such a high frequency crystal. Seems like a waste of time and the 4 mHz crystal will probably result in fairly short battery life.

If anyone can shed some light on this movement I would certainly like to know more.
 

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For better accuracy the watch needs to be worn for at least 12 hours per day.My casio 593 A159WA after worn 12 hours per day fast with 0.3s.after off worn 12hours slow 0.3s.if worn all days fast 1s.for 3days.
 

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Theoretically, at optimum temperature and if adjusted properly at the time of manufacture, the 4 MHz drift rate should be close to 6 seconds a year!
I suspect volume sales at Casio didn't permit time consuming adjustments, resulting in less than stellar performance.
 

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David, thanks very much for revisiting your Casio 4.19MHz watch. Yours is the only watch in the forum with a 4MHz oscillator! A few of the forumers have clocks with 4MHz oscillators but those ones are a bit large on the wrist...;-)
Does your Casio have a perpetual calendar?
 

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Excellent report, David. Thank you! :-! An extremely interesting piece for a collection.

In spite of the performance, given that it's one of a very few MHz watches, and a previously unknown one at that, your pics have a definite place in the "notable watches/movements" sticky. Would you mind posting there?

Thanks!
 

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Discussion Starter #6
David, thanks very much for revisiting your Casio 4.19MHz watch. Yours is the only watch in the forum with a 4MHz oscillator! A few of the forumers have clocks with 4MHz oscillators but those ones are a bit large on the wrist...;-)
Does your Casio have a perpetual calendar?
I don't think it has a perpetual calendar. No information on the watch to indicate a perpetual calendar and the instructions do not have any indication that it has a perpetual calendar. The watch does OK on a month to month basis. So apparently it has a yearly calendar.

I also have one of the 4 mHz Glashutte marine chronometers. As you mentioned, it is a little large on the wrist.
 

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Discussion Starter #7 (Edited)
Excellent report, David. Thank you! :-! An extremely interesting piece for a collection.

In spite of the performance, given that it's one of a very few MHz watches, and a previously unknown one at that, your pics have a definite place in the "notable watches/movements" sticky. Would you mind posting there?

Thanks!
I will put it in!!
 

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...So apparently it has a yearly calendar...
That's fine as for well over 2 grands the Breitling Aerospace can't do any better either...;-)
 

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Very interesting review with some good close-up pictures. Until you posted this review I wasn't aware that Casio had made a high-frequency quartz watch. Thanks for posting this.
 

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The only negative is that it should be able to keep much better time.
Can it be calibrated? I think that is the most important question. Let's say, that watch is 25 years old. Even if it was super accurate when new, the ageing of the quartz crystal has an effect on the accuracy (of course there could be other issues as well apart from ageing). If the movement has rate adjustment (calibration) option then we don't have a problem. Calibrate it for best accuracy and it won't need attention for a while. If it does not have calibration option then it's a bad design, in my opinion. I'd like to see some form of rate adjustment option under that plastic battery insulator.
 

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Can it be calibrated? I think that is the most important question. Let's say, that watch is 25 years old. Even if it was super accurate when new, the ageing of the quartz crystal has an effect on the accuracy (of course there could be other issues as well apart from ageing). If the movement has rate adjustment (calibration) option then we don't have a problem. Calibrate it for best accuracy and it won't need attention for a while. If it does not have calibration option then it's a bad design, in my opinion. I'd like to see some form of rate adjustment option under that plastic battery insulator.
I may have to open the watch up again to see what is under the battery insulator. Even if there is a calibration method, I don't yet know what it may be.

I wonder if the production of this movement may have been more of a marketing move than an attempt at better accuracy. The lack of information on the watch makes me think that it was not just a marketing thing. If it's production was only for marketing, you would think that there would be more information available on the movement.
 

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I may have to open the watch up again to see what is under the battery insulator. Even if there is a calibration method, I don't yet know what it may be...
I'd expect that the frequency of the oscillator can be re-adjusted by varying the trimming capacitor as usually were the case with megahertz-range movements. It's not as straghtforward as the digital touch-point terminals on the ETA Thermolines as it would be an analog adjustment applied to the frequency of the oscillator and would require professional-grade monitoring device like a very accurate and stable frequency-counter. Without proper monitoring device it would be a hit and miss excercise.
 

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Hi David,
I'm surprised/disappointed to hear the watch isn't keeping better time. Casios of that vintage regularly had a specification of 'Accuracy at normal temperature: +/- 15 seconds a month' in the instruction booklet. I'd guess the trimmer is the gold screw at the top of your fourth pic.
The calendar will either be set to 28 days for February (which means it just needs to be adjusted every leap year), or pre-programmed to a set date, like 2009 or 2029. To find out press the 'Adjust' button and cycle through to the date setting. If the date setting does not have a year then you've got the 28 day calendar. If there's a year set then cycle through to see how far it goes.
Here's a pic of that steel/chrome model (borrowed from Pocketcalculatorshow):

Cheers, Greg
 

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Discussion Starter #15
Hi David,
I'm surprised/disappointed to hear the watch isn't keeping better time. Casios of that vintage regularly had a specification of 'Accuracy at normal temperature: +/- 15 seconds a month' in the instruction booklet. I'd guess the trimmer is the gold screw at the top of your fourth pic.
The calendar will either be set to 28 days for February (which means it just needs to be adjusted every leap year), or pre-programmed to a set date, like 2009 or 2029. To find out press the 'Adjust' button and cycle through to the date setting. If the date setting does not have a year then you've got the 28 day calendar. If there's a year set then cycle through to see how far it goes.
Here's a pic of that steel/chrome model (borrowed from Pocketcalculatorshow):

Cheers, Greg
Thanks for the information Greg. I guess I will have to pop off the back and take a close look at that area to see if anything looks adjustable. The other photo of a Casio like mine that I referred to was the one you posted.

The Pocketcalculatorshow website is a great place to learn more about LCD and calculator watches.
 

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Not sure why but I was thinking about that watch earlier today, glad I found the thread, any luck adjusting it? Only one of two 4Mhz watches ever produced (the other one being the rare Citizen Crystron 4Mhz).
 

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Not sure why but I was thinking about that watch earlier today, glad I found the thread, any luck adjusting it? Only one of two 4Mhz watches ever produced (the other one being the rare Citizen Crystron 4Mhz).
Haven't found a way to adjust it yet.

Didn't Junghans make a 4 Mhz model?
 

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Right, don't think anyone here has that one ?

casiophile had pointed out the trimmer could be the gold screw top right on your fourth picture which seems plausible, I have an old casio that has a similar screw and turning it did seem to adjust the rate a tad, it's not exactly as sensitive as the trimmer of an Omega MQ so I need to experiment a bit more.
 

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Right, don't think anyone here has that one ?

casiophile had pointed out the trimmer could be the gold screw top right on your fourth picture which seems plausible, I have an old casio that has a similar screw and turning it did seem to adjust the rate a tad, it's not exactly as sensitive as the trimmer of an Omega MQ so I need to experiment a bit more.
I will give that a try when I get the chance.
 
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