1982 Metamec 4.19MHz quartz mantel clock, a couple of questions

Discussion in 'Electric Horology' started by Peter Planapo, Aug 6, 2019.

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  1. Peter Planapo

    Peter Planapo Registered User

    Mar 23, 2019
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    Hi all,

    A couple of days ago I picked this up at the local flea market for £5. It's not as old as most of my clocks and hasn't got a pendulum, but it'shorribly kitsch-y in an iconic 1980s way, and I thought must be one of the first mass-produced quartz clocks, so I bought it.

    On stripping I found that the ITT crystal is marked 4082, so a manufacture date of week 40, 1982. The clock was probably made within a few months of that. So was I right? One of the first mass-produced quartz clocks?

    Naturally I then read up some stuff online about quartz movements. It seems all modern mass-produced movements run at 32.8kHz and are accurate to +/- 15s/month.

    I also read that accuracy is somewhat dependent on frequency, noting the new Citizen Caliber 0100, which runs at 8.38MHz to an accuracy of +/- 1s/year.

    The frequency of this clock is 4.19MHz. Does that mean it's good to +/- 2s/year? I very much doubt it. But quartz ships' chronometers also run at 4.19MHz, and there must be a good reason for that. I've only just bought this one, and there's no second hand so checking the rate might take a month or two.

    If 4.19MHz is far more accurate why did manufacturers hit on 32.8kHz? Cheaper? I know the 32.8kHz crystals are cut as a tuning fork, called an XY cut, while the 4.19MHz crystals are cut AT. I have no idea of the significance of this. I also understand that higher frequencies need more current to run. I suppose I ought to measure the current with a milliammeter.

    About the electronics of this clock, apart from the crystal and a coil there is a chip (RCA1517P) which must I suppose be a 22-bit binary counter to divide by 2^22 (i.e. reducing 4.19MHz to 1s pulses).

    And then at the top left corner at the back of the circuit board is what seems to be a trimmer potentiometer. I judged it wise not to touch this. If it is a rate adjuster, how would one know when the correct setting was arrived at? If not what might its function be?

    Any comments welcome.

    Peter

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  2. praezis

    praezis Registered User

    Feb 11, 2008
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    Hi,

    afaik your quartz has a much better temperature performance than 32k tuning fork ones.

    You already mentioned it, 4.19M needs more base current than 32k, That and price is why 32k is pteferred today.

    How to adjust? All older quartz watch testers can test 4.19M frequency. Or use a very precise frequency meter. Else wait a few months for adjustment result :)

    Frank
     
  3. Peter Planapo

    Peter Planapo Registered User

    Mar 23, 2019
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    Thanks Frank,

    I'd be happy to use an old quartz watch tester, or a frequency counter, if it had enough accuracy. I'd say it would need an accuracy of 10 parts per billion, which is I believe around 3 seconds per year. Lab frequency counters I can afford are rather less accurate. hey may read to 8 digits but accuracy is more like 100 parts per billion or less.

    As for older testers, looking at eBay I'm confused by many quartz testers from £20 to £800, including some older ones. None mentions 4.19MHz. Could you say some examples of suitable older testers?

    I measured the running current and found just 0.2mA with brief one-per-second pulses of 0.8mA, so my clock ought to run for a year at least on a C cell.

    I also found (with a 10x magnifier) that the minute-hand retaining boss was rotating by seconds. So I pulled it out and soldered a balanced second hand to it... an easy job and I now read seconds, so will be able to measure the rate much more quickly. I wonder why Metamec didn't fit the second hand, when the mechanism was already present.

    Peter
     
  4. praezis

    praezis Registered User

    Feb 11, 2008
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    Hello,

    I use a timometer 4000.
    But also the divided 1 Hz noise or magnetic pulse can be used as a test signal.

    Frank
     
  5. Peter Planapo

    Peter Planapo Registered User

    Mar 23, 2019
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    Dear Frank,

    I'll keep my eye out for one of those. There don't seem to be many here in England, but ebay.de has a few Timometer 4500s. I read they have about 10s per year accuracy, which is better than most clocks I'm likely to get my hands on. Could one of these be used for clocks as well as watches, with an external microphone? And pendulum clocks?

    Could you please explain to my very analogue mind, what is meant by "divided 1Hz noise or magnetic pulse" and how it can be used for testing? I first thought you meant the 1Hz pulses from the clock, but obviously a signal can't be used to calibrate itself, but needs an external source.

    Since I fitted the second hand, I've timed the Metamec (using the Android Watchcheck app) to be losing 0.9s per day, 27s per month, so it's actually worse than a £1 quartz movement from Amazon. Can I try to improve the rate error with the little trimmer potentiometer on the circuit board? How sensitive might that be, and which way would it turn... clockwise for faster, anticlockwise for slower?

    Thanks for your patience,
    Peter
     
  6. praezis

    praezis Registered User

    Feb 11, 2008
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    Hello,
    what I meant is, you can use the 1 Hz that drives the stepping motor instead of the 4.29 MHz. Of course test equipment is needed in both cases.

    Frank
     
  7. JTD

    JTD Registered User

    Sep 27, 2005
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    Metamec of Dereham were the first people in Britain to manufacture their own quartz movements. The hostory of Metamec is an interesting one and you can read about the company in a book by Clifford Bird called 'Metamec, The Clockmakers, Dereham'.

    You could borrow a copy from your local library or ask them to get it in for you from another library if they haven't got it.

    JTD
     
  8. Peter Planapo

    Peter Planapo Registered User

    Mar 23, 2019
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    Thanks JTD, My library service, owing to budget cuts (of course), isn't allowed to look outside my borough for loaner copies, and there are none locally. I'll have to find one to buy, but I imagine it's a pretty rare book.

    I've been adjusting the capacitor and have now got the clock to a pretty acceptable 8 seconds/year (that's of course extrapolated; I actually measured, using WatchCheck daily, 0.4s over 19 days).

    I don't think I'll be able to do better. It's still not quite as good as NTP but no complaints for a 35 year old quartz clock that cost £5. Truth be told it surprises me... but let's see a year down the road.
     
  9. JTD

    JTD Registered User

    Sep 27, 2005
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    That's terrible. Even my library in rural Norfolk will search outside the county for a fee (about 6 pounds). I've had some pretty obscure books that way. The Metamec book is not that rare, you can find copies on Amazon, but they they are about 35 pounds. Another good place for second-hand books is: www.used.addall.com

    I'm not surprised you got a good result with the old Metamec quartz movement. They were the first company to manufacture their own in Britain and they were very well made.

    JTD
     
  10. Peter Planapo

    Peter Planapo Registered User

    Mar 23, 2019
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    My borough claims to have the lowest council tax in the country, and it is really low but as we see there is a price to pay.

    Anyway further research came up with METAMEC, THE CLOCKMAKER, DEREHAM - AHS - Antiquarian Horological Society which I lost no time in buying for £6 including postage, it's unbelievable! I thought it must be an e-book but no, it's listed as a hardback. I'm half expecting an email tomorrow telling me sorry, it was already sold, or that it was a pricing error or whatever.

    Anyway, thanks again for the heads-up.

    Re accuracy, yes well-made it certainly is, and I'm told the thermal stability is far better than 32kHz clocks, which are what you get now, and they have no adjustment either. I'd be lucky to get 10s per month from any of my newer quartz clocks, more like 20s. Going from 4.19MHz to 32kHz was a major step backwards.

    Peter
     
  11. JTD

    JTD Registered User

    Sep 27, 2005
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    Excellent! AHS were the original publishers, but I supposed that they would have sold out and that only a second-hand copy would be possible. Happy that you got a new copy and a reasonable price.

    Metamec were very particular about quality and when the cheap quartz movements came in, they couldn't compete. Also they brought out dozens of new clock models every year, too many really. It's a pity, because they were good people. as you will see when you read the book.

    JTD
     
  12. Peter Planapo

    Peter Planapo Registered User

    Mar 23, 2019
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    The Metamec book has arrived and is truly a work of completeness and magnitude. It even branches off sideways to the various Teasmade machines (I use an early Goblin for my morning coffee, so that's a great bonus).

    Since the postage was £3, the AHS have charged me all of £3 for the book itself, which must be less than the cost of printing. I suppose they are mow being remaindered.

    It promises to be a good read and I'll treasure it.
     

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