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Junghans ATO-MAT (~1960???) stopped working

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this is the "family kitchen clock": This clock is at least as old as I am.
It has a W-707 movement...an ATO-MAT, which is
kinda "pre quartz"-movement: A rotor like a BIG balance wheel is equipped with four magnets.
The first two magnets induce a voltage into a pair of coils, which in turn switches a current,
which flows through a second pair of coils, which then pulls the second pair of magnets. Since
the second pair sits a little further away on the circumference of the "balance wheel", that
wheel gets a kick, and the circle starts at the beginning again.

After 55 years of measuring the time, the ATO-MAT suddenly stops working. I checked the obvious things
like corroded battery contacts, loose cables, emtpy batteries etc but found nothing. Since this clock is there
since I am able to think I definitely want to repair it. And it would be my first clock/watch, which I try
to repair.

But before I unscrew anything...what is most likely the problem? Is there anything known
like "the typical ATO-MAT problem" or "any germanium transistor will die after 50 years" or something
like that?

I found some schematics of similiar ATO-MATs (not the W-707), which were not THAT complicated.

If it is the transistor it will be hard to find a germanium transistor these days I think...

Short description of the problem: Insert a battery, switch the starter (which is a little piece of metal, which
gives the "balance wheel" its first kick)...the "balance wheel" swings a little (looks not like it would be slowed down
by any abnormal friction or so) but the amplitude decreases rapidly until it stops.

Thanks a lot for any help in advance!


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Hi     As a rule its usually the transistor not switching on the ATO there are equivilant tables to find an alternative NPN or PNP what ever type is installed in your clock have a look on google, just type in your transistor and get a list.  The transistor you find will have a different case type so may be require modding to fit....  good luck 

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Hi Mcc   Just googled ATO-MAT W-707 and pulled up a load of info on the 707. I have up loaded a tear down on the 707 also Think the tranny is a AC125 germainiun  PNP it will probably be an old style plastic case.   Just a thought check the driving coil for being o/c, dry joints etc.       enyoy



















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Thanks a lot for all the infos! :)

I have googled before...and found quite an amount of "stuff". The problem with google and the interne is: Neither is a watchmaker or watch repair enthusiast. For example: I searched for informations about the 7S26C movement of my SEIKO 5 wrist watch. And found (for example) the following contraductionous (huuuu....this word looks horrible wrong...) informations: NEVER touch the movement with bare hands and a video in which exactly this has been done. NEVER touch _BOTH_ of the pins, which adjust/regulate the hairspring and another video, which says: that one regulates the length and the other one adjust the idle position of the balance wheel and both can be corrected of course. And the whole variations of "the right oil" to lubricate the movement. And....
You get the idea.

That's the reason for me to come to the place -- this forum -- , where the density as the chance to meet people, who DEFINETLY know, what they are talking about, and repeat the question here... :)

By the way: It seems the my W-707 runs (or better: does not run....hehehe) with a AC122. But I have to confirm this later....with a stronger light and a better lens ;) I will check the coils also...thanks for all the hints and infos!!!

My W-707 has a plastic gear.

Thank you all again! :) :) :)



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just for the little smile...
On the internet I found a company selling AC122 transistors! Guess, what other things they sell, too....
Musical instruments!
Oh yeah! Sometimes everything fits together!


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