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Discussion Starter #1
Hi all,

First post on the new look forum,

With the time change to summertime in the UK its time for quite a few of us to be adjusting quartz watches. I have a few and a bit of time on my hands at the moment.
There's also quite a few that haven't been touched since October last year and although I don't normally time watches I do set them accurately to a HTML time signal.

I may add to the list later but for now the most surprising result was:

SBBN 035 Tuna with 7C46 movement +2 secs in 6 months

In comparison my Bulova Lunar Pilot with 262 kHz quartz was +3 seconds

I can only guess I've got lucky with my Tuna.

OtherJohn
 

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Yes I entered 1000m 7C46-7009 into which I had replaced the original 7C46A with a brand new 7C46C into a quartz time keeping exercise thread on another forum. In all fairness to Seiko I did not attach it to any sort of quartz movement regularator or timing machine to trim it after mounting the dial and hands because I do not have such equipment.

As shown +8 seconds after one month I was a bit disappointed.
7EF9DF05-6691-4FE6-A6FE-85E52448FFB5.jpeg
4D69BAB5-8E86-48CA-981A-79AC9A3032A3.jpeg
 

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In my experience, websites seem to suffer from quite a bit of lag. I've cross checked them against radio-controlled watches and there was always a considerable lag.
Therefore, I would advise using a radio-controlled watch as reference when checking accuracy. You may find that the 7C46 actually performs better than the +8s per month.
 

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Yes I entered 1000m 7C46-7009 into which I had replaced the original 7C46A with a brand new 7C46C into a quartz time keeping exercise thread on another forum. In all fairness to Seiko I did not attach it to any sort of quartz movement regularator or timing machine to trim it after mounting the dial and hands because I do not have such equipment
Does the 7c46 have a trimmer? If so, I didn't realize that. And here I've been feeling smug about trimming my 7546/8 movements thinking newer watches couldn't be done...:)
 

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Does the 7c46 have a trimmer? If so, I didn't realize that. And here I've been feeling smug about trimming my 7546/8 movements thinking newer watches couldn't be done...:)
Well sort of. No real trimmer per se. There is a one-time only adjustment to the circuit block by cutting either a + or a - circuit part and apparently practically no one has ever actually done it. You to into the hole under the anti-mag plate and use any sort of tool to scrape away part of the PCB inside the hole to stop circuit flow through that loop. Once done, you are done.

The stated Seiko accuracy is +/- 15 seconds per month which clearly is not great but hey we get ourselves nuts over the littlest things.
 

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Well sort of. No real trimmer per se. There is a one-time only adjustment to the circuit block by cutting either a + or a - circuit part and apparently practically no one has ever actually done it. You to into the hole under the anti-mag plate and use any sort of tool to scrape away part of the PCB inside the hole to stop circuit flow through that loop. Once done, you are done.

The stated Seiko accuracy is +/- 15 seconds per month which clearly is not great but hey we get ourselves nuts over the littlest things.
Got it - this rings a bell now that you mention the one-time nature of the adjustment. After making this post, I took a closer look at some pictures of the movements and saw the +/-, but wasn't sure about their function. Shame the couldn't carry forward with trimmer resistors like the 7546/8 movements, but I get it...economics, and all that.
 

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Discussion Starter #9
One of my most accurate quartz watches is a 7C43, don't know if that has trimmer or not?

And since I've been checking recently one of my 7548 divers seems to be running about +4 minutes a Month. Are there any instructions on how to adjust the movement using the trimmer?

OtherJohn
 

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One of my most accurate quartz watches is a 7C43, don't know if that has trimmer or not?

And since I've been checking recently one of my 7548 divers seems to be running about +4 minutes a Month. Are there any instructions on how to adjust the movement using the trimmer?

OtherJohn
Check to see if you have a 7548A or a 7548B.
The A version can be adjusted with the trimmer.
The B has no trimmer but two traces that can be cut to change the timing. This is a one time operation only!
 

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Discussion Starter #11
Check to see if you have a 7548A or a 7548B.
The A version can be adjusted with the trimmer.
The B has no trimmer but two traces that can be cut to change the timing. This is a one time operation only!
Its a 7548A, there's a gold slotted screw next to the circuit block but the arrow doesn't say which way is + or -. Or how much to turn to reduce it from + 4 minutes/month?
 

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Its a 7548A, there's a gold slotted screw next to the circuit block but the arrow doesn't say which way is + or -. Or how much to turn to reduce it from + 4 minutes/month?
It's going to be trial and error without a proper quartz timer tool.
That being said, it requires ever so little turning of the screw. Just think about how little adjustment of the regulator on a 7s26A it takes to make a huge difference!
 

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Discussion Starter #13
Sorry I'm not that technical, do you know which way to turn for -?

Roughly how much to slow it down a little?
 

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Sorry I'm not that technical, do you know which way to turn for -?

Roughly how much to slow it down a little?
Well, I did a 7a38 for my neighbour which was off by about 30 seconds per day. It should have had a full service but I figured I would try the trimmer first. I was leary about turning the screw too much so just barely nudged it and it went too far the other way by about a minute. Over a week, I managed to corral it into running about 2 seconds per week. He's had his watch back for about a year now and it has not fluctuated.
I seem to remember turning the screw so that the slot pointed more to the + to speed it up or more to the - to slow it down.
You're definitely going to have to chase it no matter what without quartz timing machine.
 

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Discussion Starter #15
Well, I did a 7a38 for my neighbour which was off by about 30 seconds per day. It should have had a full service but I figured I would try the trimmer first. I was leary about turning the screw too much so just barely nudged it and it went too far the other way by about a minute. Over a week, I managed to corral it into running about 2 seconds per week. He's had his watch back for about a year now and it has not fluctuated.
I seem to remember turning the screw so that the slot pointed more to the + to speed it up or more to the - to slow it down.
You're definitely going to have to chase it no matter what without quartz timing machine.
Okay thanks but I can't see a + or - anywhere to know which way to turn it?
 

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Discussion Starter #16
On second thoughts its probably best if I send it to someone with a timing machine to get the best out of it. Maybe a service while its there.
 
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