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Girard Perregaux C641 Quartz Movement


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1 hour ago, MrRoundel said:

Does that make sense?

Will the crystal still pulse when there is a power supply connected, despite having an open coil?

Yes, it makes sense and yes it should pulse with no coil, however it is possible that these pulses may not be obvious, since they may involve switching a transistor, to allow the coil to conduct, and your meter may not present sufficient load to "see" the pulses, or they may look very small. A typical multimeter has a resistance in the meg ohm range, rather than killo ohm range.  You may need to put a resistor (2k Ohms or more) in place of the coil, and measure across the resistor. 

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My meter appears to have a much lower range, no? I don't expect to be able to check the crystal with it. For that I figure I'll need to step up and buy some sort of quartz watch tester that picks up the pulse. I know that my meter does not have a frequency setting. Cheers.

 

 

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On 3/23/2020 at 5:46 PM, AndyHull said:

Are you sure that is not the crystal? I suspect the coil is what attaches to those two dumbell contacts we were looking at earlier. As a matter of interest, what is the resistance between the two gold plated dumbell contacts?

Oh, I guess I can answer this question now, the coil appears to be open. And yes, you were correct about those contacts which connected to the posts that connect to the coil.

Repairing this coil would be really difficult, methinks. If you look at the image from Fried's quartz book, you'll see why. The stepping motor sits down, and is trapped, between the two sides of the coil.

 

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8 hours ago, MrRoundel said:

My meter appears to have a much lower range, no?

Not really.

The figure you are looking at is the "Impedance" figure. Specifically the impedance for the voltage ranges. This is quoted as 10M Ohms. With the coil in place, you are measuring voltage across a 2k Ohm coil, but without it, there is no load, except for the 10M Ohms of the meter, so very little current will flow, assuming the coil driving transistor conducts at all, and therefore  the pulses may be much less obvious.

Remember, you are looking for voltage pulses, so you need the meter on voltage to do this test.

You may see some activity. On my meter I see quick pulses where the readings jump about once per second.

Because the pulse is quite short, you don't see a nice 0V 1.5V 0V 1.5V transition, but it is obvious that the circuit block is doing what it should be. On some circuits, the pulses may be at 1/2, 1/4 or 1/8 second intervals, and on some (Timex 2 handers for example) the pulses may be once per minute. In your case, I think they will be in the 1, 2 or 4 pulses per second range. The service information should tell you this, but if you don't have that, then this is what to look for.

If the circuit is not working, you will probably just see a bunch of random readings hovering around a single value (random noise).

EDIT: Some (all?) quartz testers pick up the changes in the magnetic field of the coil when it is energised, and give you a beep or click every time the coil is energised.

If the coil is open, then they wont click, as there is no magnetic field. However this doesn't actually tell you what has failed, since if the circuit has failed rather than the coil, you will also see (hear) no pulses.

Edited by AndyHull
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Thanks, gentlemen. JohnR275, those book pages are priceless!  Many thanks for scanning and providing them. Paragraph "f" on page 125 would have probably saved me a bit of trouble, as it talks about prying up the circuit at the "spring contacts". Truth be told, there's not a lot of "spring" there. I guess I should have checked the coil before I installed the circuit. Oh well. I am very pleased to have this information. Again, many thanks.

And AndyHull, I guess I'm showing my ignorance on electronics. Thanks for clearing up my misconception about the meter, etc. I may reinstall the battery and check for voltage after I absorb the pages that JohnR275 kindly provided. Cheers.

On a related note, I did notice that the AWCI is holding a quartz watch webinar on 6/24. It looks like one could join in without being a member by paying a few dollars more. I'll probably give that a shot. I mention it in case someone else is interested and I am correct in my belief of non-member access.

You guys, and the WRT/WRC, are sooo dang helpful. I can't thank you enough.

 

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8 hours ago, AndyHull said:

Remember, you are looking for voltage pulses, so you need the meter on voltage to do this test.

yes technically are looking for voltage of  but  often times on analog meters if you go to the lowest current range possible the superlow microamp range you're putting the  voltage directly across the meter with nothing in the way for the most part and that gives you the most sensitive range versus the voltage range which is usually much higher.  And then I find when you're on that supersensitive range you will see the needle twitch a little bit up-and-down but of course as you pointed out the pulses are too short to actually measure anything.. bbut you do get a really good clue that you are getting pulses out..

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Interesting that the tech sheets say that you're not supposed to take the stepping motor module apart. While I didn't clean the coil and motor, I did clean the upper and lower halves with hole jewels. I can certainly understand why they say to not take it apart. It's a bit of a bear to get back together, as I think I mentioned above. 

I had to flatten the end of a brass tapered pin, put it in a pin-vise, and manipulate the motor through a small opening between the top plate and the coils. I don't think there was any copper wire from the coil exposed where I was manipulating. If there was, I may have broken a wire. Looking at the images in the Fried diagram I don't see any wires that I could have hit. I guess I'll get a look at it after I remove the circuit and test out the coil, etc. If it is indeed open, I might as well open up the housing and see if I broke it.

 

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I was able to remove the circuit without destroying it this time. I guess that's good.

Unfortunately, my worst fears are confirmed and the coil is open. I guess I'll open the housing and see if I can find a break in the wire. Thing was a royal bear to get back together last time but I suppose it doesn't matter now because it's toast.

I'm back to my "I think I may have made a mistake in buying ...". Live and learn.

At this point a quartz analyzer isn't going to tell me much that I don't already know. Bummer.

The first image shows the bottom of the stepping motor and coil assembly. The second is a  high magnification of the "bruising/breaking" of the wire next (below right) to the stepping motor itself. When I was manipulating the stepping motor with my tapered pin it was through a space at the top of the assembly, so it may not have been me who did the damage. It may have been some other fool who took the unit apart and fought with it to get it back together, damaging the coil windings in the process. Still, it is possible that I did it. 50/50 I'd say. If the watch was running before I took it apart I'd take the blame 100%. Oh well, I'll keep my eyes out for a parts movement with a known good stepping motor. I know, good luck with that, right? Thanks to all for their assistance. Stay healthy.

 

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  • 2 years later...

Boredom, and the possible availability of a parts movement for a decent price, brought me to looking at this watch again. This time I had one of the Vigor electronic watch testers that I had purchased online a couple of years ago. Unfortunately, it had a battery accident and showed a lot of salting damage at "AA" battery contacts. Ultimately I got it working, but the calibration isn't great on it. Still, I was able to touch the "dog-bone" contact points and get a reading from the circuit. It pulsed to three different positions, a higher, lower, and middle position. I don't think I can rely on what it actually read, but it did pulse as I think it should. And I did verify that the coil is indeed open...again.

Next move might be to reach out to watchmaker, Chris Radek, to see if he will re-wrap the coil.  I've considered a parts movement but have already thrown money away on one that also had an open coil, and I worry I would repeat that error. And so it goes...Cheers, all.

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