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Longines L4 620.2 Les grands classiques


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Hi all. 

I was hoping to get a reply from a member on here who has repaired one of these, but to no avail. Would anyone have any guidance regarding getting this going again.

New renata battery ( checked model and apparently correct), fitted. No signs of dirt/dust. Perhaps needs lube.

Any advice much appreciated. 

 

20230802_113712.jpg

Edited by Jonnyboy65
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At first you should inspect the rotor with a loupe (see arrow).2FA0B102-69F7-40FD-95E5-F55C2E370353.jpeg.b40e51af43dc7e236a8d5eab3572909d.jpeg

If it shows the slightest twitch every second there is a mechanical fault most likely. If not there might be an electrical issue.

An affordable tool for this kind of diagnosis is this:

AAE83F1A-BD9C-4FB1-8D6F-12725D939D29.thumb.jpeg.93ba20d3e267e615769145c35dc75e7d.jpeg

If you have a watch demagnetizer handy you can use it for moving the train components and hands. If nothing moves the train of wheels got stuck.

Edited by Kalanag
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Some of these 2 hand ladies movement do not "tick" every second like larger gents watches to conserve battery power. Instead, some only tick once every 10, 20 or even 30 seconds. 

After a new battery is inserted, you have to watch the rotor very patiently or if you have an impulse tester, you have to wait at least 30 seconds for an impulse.

Another way to test is to put both hands at 12 and see if the hands move apart.

If the gear train is stuck, just applying new oil will not solve the problem. The entire movement has to be disassembled and cleaned. If this is the first time you are working on a ladies quartz movement, this is not an easy task due to the extremely small dimensions. Best to work on a less expensive movement first to gain experience.

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1 hour ago, Jonnyboy65 said:

If the train is stuck, would it help to lube the pivots do you think?

If the train of a quartz movement is stuck it is most likely a dirt particle blocking a wheel. Lubrication plays no major role in a quartz movement which can run fine without any.

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Ahhhh, ok.

So is it common practice to cautiously suction the dirt or to equally cautiously blow it out with, say, bellows?

I'm not surprised to hear you say all that. 

I wonder if there are any good and reliable independent watch repair engineers who would have the correct knowhow and equipment to service and/or repair this timepiece??

Anyone got any suggestions?

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4 hours ago, Jonnyboy65 said:

I was hoping someone might have a bit of fault diagnosis guidance

when you are changing the battery did you make sure that the battery insulator on the other side is still in the correct location?

then for troubleshooting you really need the technical sheet which I've attached. Then you also need some electrical test equipment.

PDF page 14 as the diagnostic information but it does require the test equipment that you probably don't have.

3 hours ago, Kalanag said:

slightest twitch every second

3 hours ago, HectorLooi said:

only tick once every 10, 20 or even 30 seconds

then if you look at the tech sheet you see that it should impulse every 20 seconds or as they state three times per minute.

then test equipment like measuring the coil resistance to make sure it's not damaged. Being careful when you do that the stay away from where the leads actually touched the circuit board because you could damaged the leads right there trying to test. I've circled where you want to stay away from for testing and I circled something in the middle the coil which looks suspicious maybe it's just dust particle

image.thumb.png.a9f4fd9a9bec93a77987712e19a3ab3f.png

then personally for me I like to test the current consumption but that requires a micro amp meter and a suitable power supply.

1 hour ago, Kalanag said:

If the train of a quartz movement is stuck it is most likely a dirt particle blocking a wheel. Lubrication plays no major role in a quartz movement which can run fine without any.

we've had different experiences. Some quartz watches will run without lubrication others will not. Dirt particles dust falling of the watch will definitely cause an issue. but I usually find a holder quartz watches the lubrication's gone bad and typically it's sticky. Sticky lubrication a quartz watches is bad the watch really needs to be serviced that means complete disassembly just like a mechanical watch.

CT_210001_FDE_502580_09.pdf

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On 8/8/2023 at 4:44 PM, JohnR725 said:

when you are changing the battery did you make sure that the battery insulator on the other side is still in the correct location?

then for troubleshooting you really need the technical sheet which I've attached. Then you also need some electrical test equipment.

PDF page 14 as the diagnostic information but it does require the test equipment that you probably don't have.

then if you look at the tech sheet you see that it should impulse every 20 seconds or as they state three times per minute.

then test equipment like measuring the coil resistance to make sure it's not damaged. Being careful when you do that the stay away from where the leads actually touched the circuit board because you could damaged the leads right there trying to test. I've circled where you want to stay away from for testing and I circled something in the middle the coil which looks suspicious maybe it's just dust particle

image.thumb.png.a9f4fd9a9bec93a77987712e19a3ab3f.png

then personally for me I like to test the current consumption but that requires a micro amp meter and a suitable power supply.

we've had different experiences. Some quartz watches will run without lubrication others will not. Dirt particles dust falling of the watch will definitely cause an issue. but I usually find a holder quartz watches the lubrication's gone bad and typically it's sticky. Sticky lubrication a quartz watches is bad the watch really needs to be serviced that means complete disassembly just like a mechanical watch.

CT_210001_FDE_502580_09.pdf 4.32 MB · 3 downloads

Excellent advice, many thanks. 

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