Junghans ato-mat wall clock repair

[RealRedHair]

Hello,

Bought a nice Junghans ato-mat s electronic - W726a clock. Unfortunately it does not work so I will have to repair it. Fresh battery is in. When I start the clock by moving the left lever it turns several times and stops. If I place the battery in it turns a bit longer but will also stop. So my quick conclusion is that the electronic is fine but the whole maybe needs some oil to reduce friction. 

What are your ideas and what can I check how? All advice is welcome!

Thanks

[JohnBayley]

I'm working on one of these at the moment. Yours appears to be the exact same version as mine. There are a few variants depending on when they were made.

At the start I must emphasize that I am NOT experienced at all in clock repair. Electronics is my area of expertise so I'll just tell you what I found with mine. 

Initially, before trying to get into the mechanism, I made some electrical measurements (using an oscilloscope etc) on the current consumed while running and learned a fair bit from that (like whether the balance is operating with adequate amplitude.). My movement ran, but timekeeping was erratic and it would occasionally stop even with a new battery. 

If it clearly runs longer with a battery installed as you say, then that is a good sign for the electronics. The first thing I would try is to remove the plastic case (I had to fashion a tool to compress the time setting knob to remove it.)  Carefully clean the little brass helix on  the balance wheel shaft and the pin-wheel that it drives. Be careful not to damage the tiny detent spring on the pinwheeI rachet. I used a little isopropyl alcohol which probably flushed the lower balance pivot as well. This instantly had the movement running smoothly. It now runs all the way down to 1.0 volt before stopping.

Also check the electrical connection from the negative battery terminal to the circuit board. It is just a pressure connection I think.

I'll be interested to hear how you go.

What I would like to know from anyone reading this is should the brass helix and plastic pinwheel be oiled or left dry? If it should be oiled what oil is suitable for this? I assume a low-viscosity oil would be preferred in this application?

[Klassiker]

I have one that runs perfectly with the movement tilted slightly. I don't understand why, but it works!

[RealRedHair]

Hi, Made short video. 20231221_212005.mp4

Funny sound also. Where do I start with the repair? I thought of applying  some oil to lubricate all and reduce resistance? Good idea?

Edited December 21, 2023 by RealRedHair

[nevenbekriev]

Oiling - a good idea, but cleaning of the old hardened oil is needed first. And this is done with full dissassembling of the movement. You can put some fresh oil on the pivots of the balance for test, and may be it will start working, but soon will stop again Be verry careful with the coil - it is easy to damage by simply scratching it with something, balance magnets for example

[RealRedHair]

And some more detailed photo's: Photos

I'm not able to remove the front glass so if I remove the clock from the backside the clock hands will fall of and I cannot attach them anymore. 

But I will try little oil on pivots of balace I think. Thanks!

[nevenbekriev]

19 hours ago, RealRedHair said:

Hi, Made short video. 20231221_212005.mp4

Funny sound also.

First to do is to take out the train bridge and the wheels and leave only the balance and the PCB, then  power it and checkif it will oscillate not stopping. Look at the teeth of the wheel coupled to the balance, show pictire of it.

[Kalanag]

From a 1963 Junghans catalogue:

https://junghansarchiv.de

First year of ATO-MAT 1962

https://junghansarchiv.de

Also interesting:

http://www.hwynen.de/jgh-w794.html

Edited December 22, 2023 by Kalanag

[RealRedHair]

3 hours ago, Kalanag said:

From a 1963 Junghans catalogue:

https://junghansarchiv.de

First year of ATO-MAT 1962

https://junghansarchiv.de

Also interesting:

http://www.hwynen.de/jgh-w794.html

Thanks very much. Interesting! 

 

On 12/21/2023 at 1:40 PM, JohnBayley said:

I'm working on one of these at the moment. Yours appears to be the exact same version as mine. There are a few variants depending on when they were made.

At the start I must emphasize that I am NOT experienced at all in clock repair. Electronics is my area of expertise so I'll just tell you what I found with mine. 

Initially, before trying to get into the mechanism, I made some electrical measurements (using an oscilloscope etc) on the current consumed while running and learned a fair bit from that (like whether the balance is operating with adequate amplitude.). My movement ran, but timekeeping was erratic and it would occasionally stop even with a new battery. 

If it clearly runs longer with a battery installed as you say, then that is a good sign for the electronics. The first thing I would try is to remove the plastic case (I had to fashion a tool to compress the time setting knob to remove it.)  Carefully clean the little brass helix on  the balance wheel shaft and the pin-wheel that it drives. Be careful not to damage the tiny detent spring on the pinwheeI rachet. I used a little isopropyl alcohol which probably flushed the lower balance pivot as well. This instantly had the movement running smoothly. It now runs all the way down to 1.0 volt before stopping.

Also check the electrical connection from the negative battery terminal to the circuit board. It is just a pressure connection I think.

I'll be interested to hear how you go.

What I would like to know from anyone reading this is should the brass helix and plastic pinwheel be oiled or left dry? If it should be oiled what oil is suitable for this? I assume a low-viscosity oil would be preferred in this application?

Found a small clock shop in my town and I decided to bring the clock there. Keep you  updated on it.

 

Ah I found mine. 1971 see https://junghansarchiv.de/uploads/1971_01_0022_grossuhr_ae215bcbf0.pdf

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