1974 Citizen Cosmotron 7804

15/07/2025
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I bought this one with a plan to service and spruce up and sell on time-tees.com

On arrival although looking dull and having a scratched crystal I thought the dial looked good.

As you can see there is definitely potential under that aged crystal. I immediately removed the caseback to now inspect the movement. These are a hybrid movement with a balance wheel doing the regulation but the power coming from a battery through a board with a transistor to a coil that runs in between two wheels on the balance wheel. The coil pulses and magnets on the balance wheel are polar opposite and make the balance wheel swing. Just a great idea and largely unappreciated today.

The good news with this movement is although the battery is still installed it does not appear to have leaked. On some the battery can leak over all the components and given enough time will destroy them.
Here we have a fairly clean movement that with a good service should run fine.
Now to the most important part, that dial! what a dial! so typically 70s Japanese style. Always bright and colourful.

Just look at that! anyone would think I am into 70s watches !! gorgeous.

Next step was to strip it all down to its components, inspect, clean and then reassemble and oil where necessary. They have many layers to this watch which makes it a bit more complicated than it needs to, not that challenging but when working on your first photographs must be taken to be sure you know how to put it all back together.
Here are some shots of it being stripped down!

Notice the two wheels and the brass plate. the opposite steel plate has the magnets on it.

Notice here there is a star shaped wheel just under that cover, that is essentially the pallet fork. The impulse jewel on the balance knocks that gear and the motion is transposed down the train to the hands.

Here is the top layer of wheels, you can notice that under the next layer there many more!

Next layer, but we are not done yet as the centre wheel then has three components to it.

That’s it, fully stripped down.

Once cleaned and assembled I was able to source a new old stock original Citizen crystal. Also lightly polished the case to bring back the shine.
Really is a nice piece this one which I will enjoy for many years.

Thanks

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