7C46 rate trimmer question - Seiko & Citizen Watch Forum Japanese Watch Reviews, Discussion & Trading
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Old 02-02-2011, 08:58 PM   #1 (permalink)
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Default 7C46 rate trimmer question

I have not really timed my Tuna after replacing the movement, but it does appear to gain time. At what point would you consider using the rate trimmer to slow it down??? I realize these are rated at around 15 sec per month and I am sure my Tuna will do better than that, but right now my way cheaper kinetic seems to keep better time!
Not complaining one way or the other just curious.

Paul
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Old 02-02-2011, 09:10 PM   #2 (permalink)
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Default Re: 7C46 rate trimmer question

If I remember correctly, Luka-san once said that this rate trimmer was not to be fooled around with unless if absolutely necessary. Something to do with the risk of hitting the coil with your tool while trying to ever so slightly adjust the trimmer to the rating that you need for compensation.

Once you hit the coil with your screw-driver, you can kiss your 7C46 movement good-bye.... :'(

So in your shoes I would just forget it completely.

Good luck, though.
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Old 02-02-2011, 09:14 PM   #3 (permalink)
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Default Re: 7C46 rate trimmer question

Wasent there also something about these could only be adjusted once and that was your lot or am i getting confused with another movement ?
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Old 02-02-2011, 09:16 PM   #4 (permalink)
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Default Re: 7C46 rate trimmer question

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Originally Posted by TheTigerUK
Wasent there also something about these could only be adjusted once and that was your lot or am i getting confused with another movement ?
I guess you're right, John. I remember having read something to this efect, also. Besides from what I've wrote, there is that other problem, too.

Let's wait until Luka takes notice of this thread and have the chance to chime in. He knows 7C46's by heart.
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Old 02-02-2011, 10:24 PM   #5 (permalink)
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Default Re: 7C46 rate trimmer question

I checked the tech pdf on the movement. You either cut the + or the - pattern on the circuit block which will either make it slow down 0.26sec per day or fast 0.26sec per day. Seems not that difficult. However, you are right about the coil. Thats the reason I broke the movement the first time. I closed the movement holder not realizing it was hitting the coil, which ofcourse got damaged!!!
Paul
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Old 02-03-2011, 04:09 PM   #6 (permalink)
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Default Re: 7C46 rate trimmer question

I have a few 7C46 powered watches in my collection.
They all run differently and all run faster as my old and trusted 7548 and 7549's.
The 7C46 which is gaining the most is around 12 seconds a month, I know I can trim it down with 0.26 seconds a day x 30 = about 8 seconds a month slower, so the watch would gain only 4 seconds a month.

I will certainly not use the trimmer on the 7C46 movement, only unless there is absolutely no other solution, but I think it needs to be somewhere around 25 second of a month after checking all the usual suspects first.
Reasons:
I have never done it, but the risk of destroying the movement is there and the cutting can't be reversed. So it can be done only once. I Don't know what happens if you cut the + pattern and after that cut the - pattern.

If I still am a WIS in, let's say, 25 years..I like it a lot when my movements are still in original, very nice and good condition. Cutting in there will not help.
If my watch gains 12 seconds a month, I will set it 12 seconds behind (if it would be my only watch and 24/7 wearer), it will run 12 seconds fast in 2 months. 2 months further and the watch is about half a minute fast in a span of 4 months...How important is that in real life ? I will have set a few watches in 4 months as the Tuna is one of my daily wearers but in the weekend I sometimes take a sneek to the dark swiss side.

This weekend I was working on a 7c43 movement, just to find out how delicate this plastic movement is...if I compare this to the 7548 and 7549 movements, (which are for a great part quartz modified 6309 movements) with their adjustable rate trimmer...I prefer the old stuff.

Talking about accuracy..a while ago I bought a Sinn Ux as a Sinn enthusiast, I have the U2 and had the U1.
The Ux seemed to be "The" High-End quartz diver, found out that it was running about 10 seconds a month slow...my wife wears a SEiko SBCM023, which is almost dead on.

I guess the accuracy is a bit random, a bit luck is needed.

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Old 02-03-2011, 07:04 PM   #7 (permalink)
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Default Re: 7C46 rate trimmer question

In electronics in general, we use calibration/setting by cutting traces on the pcb, if we cut the wrong thing sometime we place a bead of solder to reconnect the trace and cut the right one. I dont know if this is do-able with this movement. Maybe contact or show the movement to a local electronics guys to see whats possible.
Just a suggestion. Also remind the guy that its plastic - maybe he can use conductive paint.

Regards,
Rob T
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Old 02-03-2011, 07:46 PM   #8 (permalink)
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Default Re: 7C46 rate trimmer question

Can the quartz crystal be replaced on this movement, or is it part of a larger component (circuit block?). If so, perhaps you'll get lucky with a new crystal.


Myles
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Old 02-03-2011, 09:11 PM   #9 (permalink)
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Default Re: 7C46 rate trimmer question

Quote:
Originally Posted by Selym
Can the quartz crystal be replaced on this movement, or is it part of a larger component (circuit block?). If so, perhaps you'll get lucky with a new crystal.
Crystal is part of circuit block.

Here is something I am just realizing after looking at some photos of a 7C46 I took some time ago- the 7C46B does not have the pattern-cutting method of regulation. Did I miss a meeting on this? The tech guide I have access to is for the 7C46A, it mentions the pattern cutting here:
[img]

It shows the underside of the circuit here:
[img]

Notice the difference with the underside of a 7C46B circuit (among other differences in the contact patterns, the IC is much smaller):
[img]

Gratuitous shots of the 7C46B movement, with and without antimagnetic shield installed:
[img]

[img]

So does anyone have the tech guide for the 7C46B, which might mention how (if possible) it is adjusted in a service environment?
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