# To hum, but not to run, that is the question.



## blu-ray (Feb 23, 2009)

My 1967 Accutron 218 ground to a halt yesterday. OK, flat battery I thought as it's been going for 10 months on what was not quite a new 344.

BUT - the watch was still humming and if I tapped it or moved it the second hand would start up again for a little while, just like a run-down spring watch.

But if it hums it must surely be running? Searching various forums suggest the indexing wheel must be damaged but that doesn't seem to be the case. I could see the wheel rotating and if that's rotating then surely the hands should be moving?

Anyway, I popped in a new battery and it's been running fine for nearly a day and is absolutely spot on. Weird? Or not?

Any explanations welcome.

Thank you.


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## Nigelp (Jan 28, 2015)

blu-ray said:


> My 1967 Accutron 218 ground to a halt yesterday. OK, flat battery I thought as it's been going for 10 months on what was not quite a new 344.
> 
> BUT - the watch was still humming and if I tapped it or moved it the second hand would start up again for a little while, just like a run-down spring watch.
> 
> ...


 look up Silver Hawk he is the expert on here when it comes to these. I had a similar problem with a Roamer that would start 15 seconds after pushing the crown in and stop 15 seconds after pulling it out. Eventually the coil packed up altogether. I think Silver Hawk does a full service and circuit for about £100. He is your best bet.


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## vinn (Jun 14, 2015)

a common falt with the original accutrons. you have the hummers, hummers that run.but the hands don't turn. one of the many problems is in the area of the canon pinion. if you are lucky --- the watch is just cold.


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## PDXWatchCollector (Nov 15, 2013)

You need a service - contact Silverhawk. He's currently in the midst of moving, and should be accepting new work again sometime later this month. His website will contain info on his status.


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## vinn (Jun 14, 2015)

> " when she espied his cloven hoof, she wept most bitterly. he grabed the fore mast with his hand - the tap mast with his knee. broke that gallent ship in half - and sunk her in the sea"


 accutron batterys; voltage and amperage is very important to that mvt.. I use a volt - ohm meter to evaluate any battery. look up accutron battery history. more important is let an expert (in accutrons) look at it !! -- ill try to find my acc. maintance manual - I will list the title. - vinn


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## blu-ray (Feb 23, 2009)

Thanks everybody for your suggestions, and my apologies for a tardy response which I will blame on the Hamburg Christmas markets!

This was my first ever Accutron and was serviced by you know who back in 2009 and has been used occasionally since then. This year in February I decided to wear it as my everyday watch and put in a newish battery expecting to get 9 or 10 months out of it. So grinding to a halt in December was not a surprise. It had run with typical Accutron accuracy of a couple of seconds a day for that period.

I put in another new battery in December and it has been worn pretty well every day since and again has run like a dream so I think I can say that there is nothing much wrong with the watch.

Which brings me back to my original query that if it hums it must surely be running therefore the second hand should move.

Now it is possible that I am mistaken and that in fact when I heard it humming the second hand did move, but in order to hear it hum I picked it up to listen. I see now I should have listened to it without touching it, and also used a mirror so I could see the hands. I'll do that next time. But my feeling is that it was humming all the time.

OR

Is it possible for a weak power source to cause an Accutron movement to hum but not have the energy to drive the hands?

Thanks again.


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## Who. Me? (Jan 12, 2007)

I can think of three options...



It needs lubrication. The tuning fork can't drive the gear train because it's seized, but I'd expect the tuning fork to stop if that were the case, so no hum


The index wheel is damaged, so the pawls (see below) have no teeth to engage with. That may happen if the hands are wound backwards and the clutch has dried up


It may have had a knock at some time while you weren't wearing it. If so there's a chance that one of the pawls has slipped out of alignment and is not interacting with the index wheel properly. The watch will hum because the tuning fork is vibrating, but the linear vibration of the fork won't be converted to rotary motion in the gear train. I think this is the most likely. It's happened to me a few times.


To explain basically how a tuning fork watch works...

The watch has two fine fingers of spring steel with jewels on the end. They are called pawls and they convert the back-and-forth linear movement of the tuning fork to rotary motion in the gear train. There are two pawls. One is attached to the tuning fork and it pushes on the circumference of a toothed wheel called the index wheel. As it pushes, it shoves the index wheel round one tooth at a time.

The other pawl 'anchors' the index wheel, preventing it turning backwards so the driving pawl always pushes the wheel round in the same direction, rather than it just getting shoved back and forth.

If either pawl is disengaged from the index wheel, the tuning fork cannot move the gear train. The watch will hum because the tuning fork is free to vibrate, but it can't drive the gear train, so the hands don't move.

If that doesn't make sense, do some googlingThere is a really good explanation on the TZ forum somewhere, where a member used blutack and cocktail sticks to illustrate how the mechanism.

the driving pawl has slipped off, it won't be pushing the index wheel round. so the tuning fork Humming means that the tuning fork is vibrating, which means that the coils are OK. The hands are driven by the gear train. To convert the linear motion of the tuning for


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## vinn (Jun 14, 2015)

I am still looking for quartz movments to install in my accutron (and omega " tuner" ) cases. then I can sell all of those tuner fork mvts..


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## blu-ray (Feb 23, 2009)

Many thanks to Who.Me? for his descripton of the tuning fork movement.

The watch is running perfectly. All I have done is fit a new battery which I expected to have to do. I think the watch is just fine.

I think my question now is really just this: is it possible for a weak power source to cause an Accutron movement to hum but not have the energy to drive the hands?


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## Moustachio (Feb 3, 2011)

I am by no means an expert, and this is just guessing/thinking out a loud! But:

http://www.elektron.demon.co.uk/works.html

"When a new cell is inserted into the watch the capacitor is initially un-charged and looks like a short circuit. This means that there is only the sense coil in series with the base of the transistor to ground. This constitutes a resistance of about 2.25 k Ohm and so an initial base current pulse of about 0.5 mA flows (1.35-0.3/2.25K). This is easily enough to drive the transistor into saturation and send a correspondingly high current pulse through the drive coils. If we assume that only about 0.1v is dropped across the transistor then we can calculate (knowing the resistance of the drive coils is about 16 k Ohm) that the initial drive current is some 63 uA or five times the normal impulse. This gives a sufficient 'kick' to the tuning fork to start the movement. The circuit then rapidly settles into its steady state and the voltage on the base of the transistor rises to an average value of just above the turn on voltage (ie slightly more positive than would be needed to turn on the transistor)."

Which might suggest a hum before run? BUT, it is a mechanical drive, so as soon as the fork starts vibrating to produce the hum, then surely it should start turning the mechanical movement... even if slowly. Unless the movement of the forks was enough to produce an audible hum (was the pitch noticably lower than when running on full battery?) but not enough distance to move the pawl finger in and out of the index wheel to engage the teeth correctly to rotate the wheel!? The only other thought is that the hands were somehow stuck briefly!!?

(sorry not massively helpful, but an interesting conundrum!)


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## blu-ray (Feb 23, 2009)

Thanks Moustachio, the best suggestion so far I think. The fork is vibrating but not vigorously enough to cause the pawl finger to move sufficiently to rotate the index wheel by one tooth. Any advance on that? I would think that at any one time there are many Accutrons out there in a run down state. Is that stopped Accutron in your collection actually still humming?


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## Who. Me? (Jan 12, 2007)

blu-ray said:


> I think my question now is really just this: is it possible for a weak power source to cause an Accutron movement to hum but not have the energy to drive the hands?


 I'd say no. but put a new battery in and prove me wrong.

If that doesn't fix it, take the back off (beware of the coil leads, they're exposed and easy to accidentally break in an Accutron), get a decent magnifying glass or loupe and look for the pawls. Check that they're both in the correct position (Google for images). If they're crossed and/or one has slipped in front or behind the index wheel, that's your problem.

I have an Omega Seamaster f300 with the ESA-derived tuning fork movement that had this problem. I put it in in a case my luggage when we went on holiday and the baggage handlers must have dropped the bag. It stopped but was humming. When I checked the pawls, one had slipped behind the index wheel.*

If your problem was due to low battery power causing the tuning fork to push on the index wheel without enough force to turn it, I'd expect it to rapidly wear on and ruin one or more teeth on the index wheel.

*I was able to fix that problem by stopping the movement and extremely carefully maneuvering the problem pawl back on to the index wheel using a cocktail stick. I wouldn't recommend that unless you're confident that you know your way around the movement though. Lots to damage.


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## blu-ray (Feb 23, 2009)

I put in a new battery on 1st December and the watch has been going like a train since then. I think the next time I see this happen I will take more careful note of what is actually going on. Thanks everyone for your input.


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## Always"watching" (Sep 21, 2013)

What an absolutely fascinating thread. I myself have never managed to buy an Accutron watch and I am really interested to hear how these work. Also, I must say that this thread is an exempar of how the forum can operate, with helpful advice, interesting factual information and even the name of an expert who can service a particular type of watch - Brilliant!


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## vinn (Jun 14, 2015)

did you know? the history of accutron? an amazing story, but a bussines failure, and not the best movment for a watch. much like the "scripto view cigarette lighter" --- a very collectable item. - vinn


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## blu-ray (Feb 23, 2009)

I'd say to any watch collector that an original Accutron is a must. A unique movement and with the watches coming in so many different styles that you will surely find one you like. Is it the best movement for a watch? I don't know, but the timepiece in question here is just shy of 50 years old, still looks good, and keeps time to 2 seconds a day.

There's even an Accutron sitting on the moon. Beat that!

I'd never heard of scripto view lighters but now I want one and I don't even smoke!


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## Toast (Jan 3, 2016)

Once again I'm amazed by the knowledge of these chaps on TWF.

l have a two Bulova watches that no longer work, one is a Waltham, them other

is a Mondia. I also have plastic Commodore which did work, and my best one

is a Jaeger Le Coulture 1972 quartz movement. Any info please.


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## PC-Magician (Apr 29, 2013)

> What an absolutely fascinating thread. I myself have never managed to buy an Accutron watch and I am really interested to hear how these work. Also, I must say that this thread is an exempar of how the forum can operate, with helpful advice, interesting factual information and even the name of an expert who can service a particular type of watch - Brilliant!


 If your ever in the market for one then drop me a line, I am sure we could do a deal.


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