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Old 4th May 2021, 6:28 pm   #1
Jamey80
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Default Metamec A909 clock- broken coil

My lovely old Metamec synchronous clock was working, now it's not. The coil has gone open circuit- it's visually in good shape, but clearly there's a break in it somewhere.
Anyone know where I can get it rewound, or even better get a new one?
Within the EEA would be ideal but if it has to go to the UK I'll find a way.
Thanks!
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Old 12th May 2021, 7:39 am   #2
jonnybear
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Default Re: Metamec A909 clock- broken coil

I think you will either have to buy a similar clock and use as a donor, or rewinding is a possibility but probably expensive. I think if it were mine and I wanted to keep it, I would fit a Quarts alarm movement, at least cosmetically it would look the same if using original hands.

https://www.ebay.co.uk/itm/264826351...IAAOSwmOJZ9Bzv.

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Old 12th May 2021, 8:15 am   #3
Brigham
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Default Re: Metamec A909 clock- broken coil

I'm normally four-square against throwing away the original clock, and fitting something else in the cabinet.
But in this case...
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Old 12th May 2021, 8:33 am   #4
Mike Phelan
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Default Re: Metamec A909 clock- broken coil

There are a few folk on here who can rewind a coil - as it looks in good condition otherwise, please don't destroy the clock and stick its case into a dreadful quartz movement!
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Old 12th May 2021, 10:37 am   #5
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Default Re: Metamec A909 clock- broken coil

I wouldn't have thought a rewind on this would be too expensive to get done.

You could probably rewind it yourself with the right specs. I doubt you need high levels of precision. You can get cheap chinese coil winders that might be suitable.

I do agree it would be a shame to scrap the movement over this.
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Old 12th May 2021, 10:41 am   #6
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Default Re: Metamec A909 clock- broken coil

Some people rewind with thicker wire and power it from a small transformer.
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Old 12th May 2021, 10:53 am   #7
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Default Re: Metamec A909 clock- broken coil

See here:-

https://sound-au.com/clocks/ocm.html

I rewound my Goblin Time Spot clock to be 12 volt.
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Old 12th May 2021, 1:33 pm   #8
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Default Re: Metamec A909 clock- broken coil

Quote:
Originally Posted by FIXITNOW View Post
See here:-

https://sound-au.com/clocks/ocm.html

I rewound my Goblin Time Spot clock to be 12 volt.
Thanks for that, very informative, I might do it with one of my clocks here
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Old 12th May 2021, 6:23 pm   #9
Brigham
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Default Re: Metamec A909 clock- broken coil

Quote:
Originally Posted by PsychMan View Post
Quote:
Originally Posted by FIXITNOW View Post
See here:-

https://sound-au.com/clocks/ocm.html

I rewound my Goblin Time Spot clock to be 12 volt.
Thanks for that, very informative, I might do it with one of my clocks here
It's just as easy to rewind it properly, and avoid the risk of having a Chinese power-pack permanently connected to the mains.
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Old 12th May 2021, 7:57 pm   #10
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Default Re: Metamec A909 clock- broken coil

Quote:
Originally Posted by Brigham View Post

It's just as easy to rewind it properly, and avoid the risk of having a Chinese power-pack permanently connected to the mains.
I constantly admire the skills of those 20th century coil winders who managed consistently to wind so many thousands of turns of extraordinarily fine wire.

My experience has been in pickup heads rather than clocks, but even the best coil winders today struggle to achieve more than 25% of the impedance of the original coil.

Am I alone? What’s the experience of other members?

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Old 13th May 2021, 6:16 am   #11
FIXITNOW
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Default Re: Metamec A909 clock- broken coil

Quote:
Originally Posted by Brigham View Post
Quote:
Originally Posted by PsychMan View Post
Quote:
Originally Posted by FIXITNOW View Post
See here:-

https://sound-au.com/clocks/ocm.html

I rewound my Goblin Time Spot clock to be 12 volt.


Thanks for that, very informative, I might do it with one of my clocks here
It's just as easy to rewind it properly, and avoid the risk of having a Chinese power-pack permanently connected to the mains.
It.s AC so there is no Chinese or other worldly make, just a good old transformer.
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Old 13th May 2021, 6:57 am   #12
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Default Re: Metamec A909 clock- broken coil

Or a capacitor dropper, that way you wind the coil with as much of your smallest wire you can and use a small capacitor it may even fit in the case.
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Old 13th May 2021, 8:34 am   #13
PsychMan
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Default Re: Metamec A909 clock- broken coil

Quote:
Originally Posted by FIXITNOW View Post
Quote:
Originally Posted by Brigham View Post
Quote:
Originally Posted by PsychMan View Post

Thanks for that, very informative, I might do it with one of my clocks here
It's just as easy to rewind it properly, and avoid the risk of having a Chinese power-pack permanently connected to the mains.
its AC so there is no Chinese or other worldly make , just a good old transformer
Yep, plenty of quality mains transformers available . I actually have loads already in my supplies, I always save older power bricks for making my own linear supplies
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Old 13th May 2021, 12:30 pm   #14
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Default Re: Metamec A909 clock- broken coil

Thanks for the suggestions- I hadn't thought of buying a coil winder myself but I'll check it out
I'd rather keep it mains then I won't have to change the lamp in it but low voltage is an option if I'm doing it myself. Quartz no- in my opinion that would be vandalism, not a repair.
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Old 14th May 2021, 8:16 pm   #15
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Default Re: Metamec A909 clock- broken coil

I realise that this will not be useful to many folk (they won't have the parts), but what I do in such circumstances is build a coil winder out of my Meccano, and guide the wire between the reel and the bobbin being wound by passing it between my fingers. There is a knack to it, but it is cheap if you have the bits
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Old 16th May 2021, 10:17 am   #16
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Default Re: Metamec A909 clock- broken coil

The wire gauge can be thinner than hair and very difficult to wind. I'm not sure if these fine gauges of wire are obtainable.
If you can rig something up it may be possible to wind it onto a spare spool until you discover the break. It can then be joined and insulated with varnish and rewound back onto the original former. The process demands great patience and care and I must admit I would not consider it for a small clock. It's a labour of love too far!
I have rewound gramophone pick ups with such thin wire that you have to place a white card behind the wire to actually see it! I have managed around 1.5K which is more than enough for a decent sound. The clock coil is very similar. John.
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Old 16th May 2021, 2:19 pm   #17
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Default Re: Metamec A909 clock- broken coil

Would the coil from a small microwave fan motor fit?

I have measured one. bobbin 34mm long. Core 12x10mm max.

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They seem to be a pretty universal item, and you might salvage one from a scrap microwave for €0, but they are cheap enough to buy new,

18W is rather more than your clock consumes but I think it will be rather less without the shaded pole motor losses.
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Old 16th May 2021, 2:50 pm   #18
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Default Re: Metamec A909 clock- broken coil

Good thought Graham but the wire is too thick. To give some idea this picture shows a thread of the thinnest cotton I could find compared with the gauge of wire I have used for gramophone pick ups. The wire used to wind the clock coil is around 50% thinner! Quite how they manufacture it is a miracle.
Obviously a clock has to be the lowest possible consumption. I guess this will be around 3w and any wire thicker than this will consume a considerably higher current over a year. J.
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Old 17th May 2021, 12:11 pm   #19
Jamey80
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Default Re: Metamec A909 clock- broken coil

If I unwind it gently on to a suitable bobbin as far as the break, would I damage the insulation on the wire or would it be ok? Not sure how much you can flex enamelled wire, but reusing it would avoid problems sourcing a replacement.
Looks like I'm going to need to find some meccano.
I will protect it with a 20mA fuse if I rewind it like this- don't want it catching fire if I screw something up!
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Old 17th May 2021, 1:38 pm   #20
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Default Re: Metamec A909 clock- broken coil

I must admit that in these circumstances I would just fit a quartz movement. This is a relatively modern clock and would have been made on the cusp of the quartz era anyway. Rewinding the coil is going to be very difficult, especially if you have no experience of such things.

You could retain the original movement and refit it if you come across a suitable coil in the future.
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