What Makes This Cosmotron Special?

There are a number of things that can make a watch ‘special’ – it may be an expensive high grade piece, or it might be a rare vintage model; it may have been a ‘world first’, or it may have some interesting features. But in my opinion there is one thing that makes a watch extra special – and that is when the watch belonged to someone important to you and after they are gone it is handed to you. It really doesn’t matter whether or not it has any of the other ‘special’ features – the valuable thing is that you have something that a loved one previously used for many years, and their memory stays very much alive.

Why am I making this point now? Well, a chap called ‘Jay’ recently visited the blog and told me that he had inherited a Cosmotron from his late father-in-law. Jay’s mother-in-law had given the watch to him and it was the first time he had seen or heard of a Cosmotron. I thought it would good to commemorate Jay’s father-in-law through this post, and to thank him for choosing a Cosmotron all those years ago – and  for looking after it too, so we can admire it today!:

JaysCosmotronThe watch is in great condition with the case looking good for its age – very nearly 40 years – and the glass is excellent too. In fact Jay’s friends thought he was wearing a new watch when they saw it 🙂  The dial is very nicely finished with blue fading to silver in the centre over a curving texture – I imagine this one looks even better to the eye than in Jay’s photos. Jay’s father-in-law certainly has my respect for caring for this watch so well.

The case back tells us this is powered by the 7804A electro-mechanical movement, which runs at 36,000 beats per hour and was one of the later generation Cosmotrons. It was made in February 1974:

JaysCosmotronBackThe back is secured by a screw-in ring, and has a locating lug (see between the top lugs) which means the back is always in this position.

At first Jay found there was a problem, as the old battery had leaked slightly. But he was able to clean it out and a new battery saw it fire up. Great news after a long period of non-use 🙂

However, Jay then found it would not run consistently, sometimes stopping, sometimes running twice as fast as it should.  Jay is a resourceful guy though, and after consulting the reference information and diagrams on my Cosmotron page he was able to effect a repair – namely re-soldering a capacitor connection, and the watch is now running just fine. I must say that I was very pleased that my blog helped him solve the problem 🙂

Thank you Jay for letting me do a post about your watch – you have a technically interesting piece in very good condition, but more importantly you have a very nice heirloom through which you can remember your father-in-law. Wear it in good health.

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6 Responses to What Makes This Cosmotron Special?

  1. Jay says:

    Finally! After more than two months and countless adjustments, I have finally calibrated this watch to within +/- 1 second per day in reference to http://www.time.is atomic clock, for good.

    Been using it for more than a week now and it still is accurate to within a second. I could not be more than happy. All it needed was a small piece of masking tape to secure the balance wheel calibration screw from moving.

    • sweephand says:

      Hi Jay, that’s very impressive time-keeping 🙂 Your perseverance has clearly paid off. And the use of tape to keep the screw still is an interesting way of resolving that issue – I don’t know what the purists would say about that, but if it works….;)

      Thanks for the update, much appreciated. Is it ok if I do a little post on the home page about this?


  2. Jay says:

    Certainly Stephen 🙂

    I guess a piece of tape would be better than loctite or some kind of thread lock. Which makes me think, does the calibration screw have some kind of thread or is it really like a cam profile that changes the balancer spring tension?

    • sweephand says:

      I agree that loctite or similar would not be a good idea. There is a risk it could contaminate the hairspring, and of course you do want to be able to turn the screw if further adjustment is needed at some time. The adjuster does us a cam – here’s a scan of the relevant bit of the movement diagram – the screw / cam is part #056:


  3. B.Srinivas says:

    What’s the price & where to buy?

    • sweephand says:

      Hi, thanks for visitng my blog. Just search eBay with ‘Citizen Cosmotron’ and you’ll find examples and see the prices. Ignore those where the seller is asking ridiculously high prices!! If you are looking specifically for the ‘Special’ version, then make sure that there is a button at the 8 o’clock position. Stephen

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