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-   -   Metamec A909 clock- broken coil (https://www.vintage-radio.net/forum/showthread.php?t=179729)

Jamey80 4th May 2021 6:28 pm

Metamec A909 clock- broken coil
 
5 Attachment(s)
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!

jonnybear 12th May 2021 7:39 am

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.

John

Brigham 12th May 2021 8:15 am

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...

Mike Phelan 12th May 2021 8:33 am

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! 8-o

PsychMan 12th May 2021 10:37 am

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.

Refugee 12th May 2021 10:41 am

Re: Metamec A909 clock- broken coil
 
Some people rewind with thicker wire and power it from a small transformer.

FIXITNOW 12th May 2021 10:53 am

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.

PsychMan 12th May 2021 1:33 pm

Re: Metamec A909 clock- broken coil
 
Quote:

Originally Posted by FIXITNOW (Post 1373434)
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 :)

Brigham 12th May 2021 6:23 pm

Re: Metamec A909 clock- broken coil
 
Quote:

Originally Posted by PsychMan (Post 1373492)
Quote:

Originally Posted by FIXITNOW (Post 1373434)
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.

Hartley118 12th May 2021 7:57 pm

Re: Metamec A909 clock- broken coil
 
Quote:

Originally Posted by Brigham (Post 1373614)

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?

Martin

FIXITNOW 13th May 2021 6:16 am

Re: Metamec A909 clock- broken coil
 
Quote:

Originally Posted by Brigham (Post 1373614)
Quote:

Originally Posted by PsychMan (Post 1373492)
Quote:

Originally Posted by FIXITNOW (Post 1373434)
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.

merlinmaxwell 13th May 2021 6:57 am

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.

PsychMan 13th May 2021 8:34 am

Re: Metamec A909 clock- broken coil
 
Quote:

Originally Posted by FIXITNOW (Post 1373703)
Quote:

Originally Posted by Brigham (Post 1373614)
Quote:

Originally Posted by PsychMan (Post 1373492)

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 :thumbsup:

Jamey80 13th May 2021 12:30 pm

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 :thumbsup:
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.

trsomian 14th May 2021 8:16 pm

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

Heatercathodeshort 16th May 2021 10:17 am

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.

rambo1152 16th May 2021 2:19 pm

Re: Metamec A909 clock- broken coil
 
3 Attachment(s)
Would the coil from a small microwave fan motor fit?

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

Attachment 234187 Attachment 234185 Attachment 234186

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.

Heatercathodeshort 16th May 2021 2:50 pm

Re: Metamec A909 clock- broken coil
 
1 Attachment(s)
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.

Jamey80 17th May 2021 12:11 pm

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!

paulsherwin 17th May 2021 1:38 pm

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.

Hartley118 17th May 2021 2:14 pm

Re: Metamec A909 clock- broken coil
 
Quote:

Originally Posted by Jamey80 (Post 1375070)
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!

If you were to find the break early on in your unwinding process, I guess it would be worth checking the resistance of the remaining coil and comparing it with the resistance of the removed wire. That would give you an idea of the appropriate transformer ratio required to run the clock, or even a series lamp or capacitor.

I guess though that Murphy's Law would ensure that the break turns out to be near the centre of the coil. In that case, as already suggested, a rewind with a manageable thicker wire gauge and running from a lower voltage transformer would work, Maybe 110V?

I guess that none of this is economically sensible, but we all know what it's like to get one's teeth into a technical challenge!

Best of luck.

Martin

Jamey80 20th May 2021 8:13 am

Re: Metamec A909 clock- broken coil
 
I note that there seems to be some disagreement here about how old something has to be to be valuable or worth looking after. For my part, I don't care what it's worth as I'm not going to sell it, I want to enjoy it, and anything worth keeping is worth looking after.

Time doesn't stop, despite what this clock may currently be claiming, and everything will become old eventually.

Station X 20th May 2021 9:00 am

Re: Metamec A909 clock- broken coil
 
I've successfully rewound simple coils using a hand drill held in the bench vice with the coil former mounted on a piece of rod held in the chuck. I've also heard of something similar being done with an electric screwdriver.

The trouble with any form of powered coil winder, when winding thin wire, is that the wire tends to snap due to the sudden jerk when the motor is started.

If the wire is wound off a rotating spool this can also put strain on the wire. For this reason spools of wire generally have curved end cheeks so that the wire can be pulled off the end of the spool without having to rotate it.

paulsherwin 20th May 2021 10:00 am

Re: Metamec A909 clock- broken coil
 
You may be able to rewind the coil using a sewing machine bobbin winder.

Perhaps the best compromise is to rewind the coil with thicker wire for 6V or 12V operation, and power the clock using a transformer in a wall wart. Some people like to convert synchronous clocks to LV operation simply for safety reasons, and there is plenty of info around if you google.
Quote:

Originally Posted by Jamey80 (Post 1376123)
I note that there seems to be some disagreement here about how old something has to be to be valuable or worth looking after.

I don't think there are any real disagreements, just several alternative solutions depending on your priorities and expertise.

Jamey80 24th May 2021 10:40 am

Re: Metamec A909 clock- broken coil
 
1 Attachment(s)
I found a break!
This is the unspooler I made out of a coat hanger and a lint roller... It's a bit ugly but it works, the handle is a friction fit so plenty of slip if the wire gets stuck.
I'm getting 4.3kΩ resistance through the wire on the cardboard tube (that's 513m of wire, counting the turns (3950) and circumference of the tube (0.13m), or 12800ish turns of the coil) but unfortunately still open circuit on the remaining coil, so I guess I need to keep going.

Nickthedentist 24th May 2021 12:50 pm

Re: Metamec A909 clock- broken coil
 
I would definitely try re-winding it with thicker wire for low-voltage operation.

It's not difficult to do, using the original bobbin on some kind of mandrel, and spun slowly using a cordless drill.

Rewinding with original wire would challenge even very experienced winding experts.

I love your way of unwinding the coil, by the way, well done!

Jamey80 24th May 2021 3:26 pm

Re: Metamec A909 clock- broken coil
 
Thanks! Low voltage operation with thicker wire is definitely an option on the table, along with rewinding with new wire of the same spec or rewinding the original wire. I think I could do with a resistance reading on the remaining wire to work out how much of any replacement I need.

ex 2 Base 24th May 2021 5:23 pm

Re: Metamec A909 clock- broken coil
 
I made a coil winder using a lathe on very slow speed, I fitted an inverter several years ago. I made a ring using Tufnell which fits around the partially open chuck jaws, in the Tufnell I inserted/fitted a small magnet. In between the ways of the lathe bed sits a small block of wood, which has a reed relay attached to it. I did a surgery job on a £1 calculator so that as the lathe rotates, the turns are shown on the calculator display. It works both ways, I've wound coils for motor starters using used wire and removed windings so that 415 volt starters will operate on 240. Ted

Jamey80 6th Jun 2021 4:16 pm

Re: Metamec A909 clock- broken coil
 
I finished unspooling it... I calculate that the wire was about 900m long and has a resistance of 8.4Ω/m making it SWG47/AWG44 according to google.
It did break several times in the process so the original wire's not going back on, so I guess it's a choice between rewinding with the same gauge wire or less of something more manageable. I've not decided, but SWG47 wire may drive me insane...


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