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Accutron not humming--components seem OK

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1 hour ago, nevenbekriev said:

The short connections that You describe are possible, but it is not dangerous for the coils and even for the entire ciruit. The resistance of the coils is big, so the  battery voltage can not produce enough current to destroy anything. No normal multimeter can do any harm too.

You are right. It is not possible due to the huge resistance in watch coils (i measured about 2K-6K in mine). I confused the coils for being small L inductors, which usually have very tiny resistance.

@LittleWatchShop so maybe the culprit for the burnt watch coils is ESD via touch at the points mentioned? 600V of ESD should do it for 150mA into a 4Kohm coil.


8 hours ago, Neverenoughwatches said:

In my younger days tinkering with cars i had plenty of belts from petrol engine ignition systems running at tens of thousands of volts.

🤣 Yeah cars generate insane voltage, but the amps are low. I watch Electroboom sometimes to learn what not to do:


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I doubt ESD would be able to destroy a coil.

The problem of open Accutron coils has always baffled me. Even if 1.55V were to be applied directly to the coil, it shouldn't be able to fuse the wire. And if anyone noticed, it's always the cell side coil that fails.

So is it a design fault that's causing that coil to burn? Maybe as the components age, the waveform changes and creates more back EMF?

Maybe @LittleWatchShop could investigate the cause of the failure and solve the mystery.

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58 minutes ago, HectorLooi said:

it's always the cell side coil that fails.

This coil has been failing since basically the beginning of time. Basically it's not a new phenomenon the prevailing theory way back when was that because jewelry stores and other people change batteries that's why that coil is the first to go out. So basically they were all gone a very long time ago way before any other component in the watch.

59 minutes ago, HectorLooi said:

Maybe as the components age

Somewhere but I don't remember where that I don't remember exactly why but there was a reference to the protective coating would cause a failure I'm guessing where the wire is soldered to whatever it's soldered to. So I suppose conceivably if the protective coating should change its size like shrink it could pull away and because the wire to break probably just about anywhere unfortunately.


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1 hour ago, nevenbekriev said:

Yes I agree, the coils doesn't burn at all, but the wire breaks due mechanical deformation of coil or another possible reason - the flux, used when soldering, has been not cleaned entirely and etches slowly the copper till it is broken.

But why does the etching prefer the cell side coil?

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