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Discussion Starter · #1 ·
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Just finished repairing my 12th accutron this week ( I usually wait until I have a group of them to do) and it took me over a day to get one it to stop "double indexing". I phased it at 1.3 volts and it still continued to double index. I changed both coils, fork, and index wheel and still had the same problem. I then changed one of the fork spacers, and it now works like a watch! I phased the watch to 1.6 volts and it runs perfect! I have been repairing accutrons for many years and this is the first one that I have come across like this. I called the customer, and he told me he sent it out to an "Ebay" watchmaker, and it ran fast when he got it back. :T
 

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Welcome to the forum and thanks for the interesting post! Most of us here run our Accutrons with the 1.5v silver oxide batteries with out issues. I tried a few Accucell-1 batteries. One thing is that they won't run as long because of the smaller battery. Some folks have trouble getting the watch to run at all on them. I won't use them again.
 

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SAME here. 1 of 20 of mine needs Accucell, which I don't have because it died.

I find if curious that replacing the tuning fork spacers stopped the double indexing. The magnetic field should not be affected that much by the spacers. I thought they were just for clearance issues with the tuning fork possible rubbing. Maybe raising or lowering the index fingers that slight amount caused it to not slip or jump, but that adjustment can be made without removing the tuning fork. Sounds like it took over a day :)

I'll have to do some investigating... I have never considered this, touche
 

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True, and I'm not an electrical engineer. I think most coils fail because people put the wrong battery, or take it to the wrong "guy that can fix it". I do understand the basics and that increases current by 15% as well. I've yet to have one die. They have been operating on 1.5v for over a year now. We need somebody who knows more to comment. I like to keep low moisture (obviously) and keep them in midrange temps
 

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edit** I want to go back to school for electrical engineering

Failure modes of electronics - Wikipedia, the free encyclopedia

I can see overtime, fatigue possibly causing cracked solder joints and bridged capacitors and resistors. I think the actual coil is safe unless it is somehow broken mechanically. Someone posted a while back about replacing coil components and revivng coils. It was inspirational. Who wants to build a large scale accutron utilizing a life-size tuning fork, modern electronics, and visible indexing... life goal
 

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hold on.. 1.5 vs 1.3 is ~15% more!
Do you want to risk your precious coils?
Thousands - probably over a million - folks are using the 1.5v silver oxide batteries in their Accutrons around the world. While component failure has much been discussed, actual scientific testing and proof is just not there, just supposition. I understand the concern and have seriously thought about it but have decided, for my watches, not to bother any more with the Accucell battery. I do, however, respect the decision of others who still use them.
 

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Discussion Starter · #9 ·
Current in a watch battery has always been a concern. I dug up my Accutron repair notes from 1979, and they list the current of the 218 battery as 70 mAh. The 387S battery has a current of 60mAh and the 344 has a current of 100 mAh. This is why I only use the 387S battery in all my watches or repairs.

Back to the double indexing, this watch double indexed at 1.3 volts which is the original phasing voltage of the watch, not 1.5 that some seem to double index today with. The watch has been running great for the past 2 days, but I will be taking it apart today, and change the spacer back to the one that came with the watch to verify if this was the solution to the problem.
 

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I believe the mAh just refers to the life of the battery. The current is regulated by whatever voltage is supplied by the battery divided by the resistance of the accutron coil itself. A 60mAh battery can have 60mA of charge drawn from it over an hour. If the current in the watch while it was running was 60mA, our watches would only last an hour. 100mAh can supply up to 100mA per hour (again, this is not the case because of the constant voltage and resistance), thus would last longer.

That way, you can easily find the life of a battery by dividing the mAh rating of a battery, by the current through the coil.
 

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Like Oliver I respect the decision anybody makes re the battery to use but I've been using 1.5 volt batteries in some of mine for some time with no problems. My first Accutron that I bought in 1974 has been running on 1.5 volt batteries since 2007.
 

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I understand your frustration at phasing Accutrons. But, there is a scientific approach to this which minimizes problems and will get 99% of Accutrons running happily on 1.55v Silver Oxide batteries. I have been repairing Accutrons for 20+ years, and these days I have very few that can't be made to run ok. All you need to know is contained in the following page:

http://members.iinet.net.au/~fotoplot/accphs.htm

Although on the surface, the index mechanism is simple and straight forward, there are some subtleties that need to be understood clearly, and when you do that, Accutrons are no longer the problem they can otherwise be.

Bulova tested their circuits at voltages higher tha 2v, the slight increase in voltage over the original 1.35v mercury batteries is of no consequence to the life of the coils. The transistor itself is the component most likely to fail due to voltage, and we are working well within their designed range.

Regards, Rob
 

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Discussion Starter · #13 ·
I have been using this procedure that Rob has spelled for over 6 months. It works great! I have completely eliminated the Accucell and use nothing but the 387S battery. I still have not had a watch using this procedure that I could not get to run with this battery.

As far as voltage, I took a 218 and applied 2 volts from an external power supply and ran it for 6 months. I removed the power supply, put in a fresh 387S battery and it continues to run perfectly and keeps great time.

Thanks, Mike
 
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