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I have an antique clock that I am trying to get up and running. I'm told that it needs a new coil, as power is getting to the coil, but not through it.

I'm struggling to find anyone to make a new coil/repair the old one as it too small a job for the bigger companies and I can't find any smaller operations online.

Does anyone know where might take on a small coil making job? I'm in Edinburgh, but happy to have it done anywhere. Alternatively, if there's anyone on here who can deconstruct and replicate an old coil and fancies the job, that'd be great.

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toolic
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John Drummond
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    There are people who fix electric motors, usually they can repair the coil by replacing them with a new one. This would be a similar job for them. – Lior Bilia Aug 22 '23 at 10:40
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    You could try your local amateur radio club. You might find someone with a coil winder that will do the job for a bottle of their favorite. It’s probably a couple of hours work to rewind it, so at commercial rates it would be uneconomical. – Kartman Aug 22 '23 at 11:02
  • What is the wire diameter? – Spehro Pefhany Aug 22 '23 at 12:33
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    For an excellent forum that supports discussion and has members worldwide, look at http://www.piclist.com (don't be put off by the presentation or the PIC in the name). Then visit http://mailman.mit.edu/mailman/listinfo/piclist, join the mailing list & say hello. Provide as much detail of your requirements as possible. Just like here, there are people there who know almost everything (collectively). The site supports a conversational approach. Some SE members are also PICList members (myself included). It's a very useful complement to this site for questions of this sort. – Russell McMahon Aug 22 '23 at 12:50

4 Answers4

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Before you do anything else, check to make sure that the coil is bad. That would greatly surprise me. There shouldn't be enough current through it to damage the wire.

Make sure that the connections at each end of the coil are OK. Measure the resistance from one end of the coil to the other. It may be several hundred ohm to several thousand ohms. If it shows tens or hundreds of thousands of ohms, then it may be broken.

It is possible that the coil is short circuited. The enamel on the wire in the coil may have started flaking off, allowing the individual windings in the coil to make contact. That would make the resistance of the coil lower, but you'd have a really hard time telling if a low resistance is too low.

If you are absolutely certain that the coil is bad then your options are to find a replacement (not likely unless you can find an identical clock with a good coil,) or to rewind the existing coil. This is absolutely not rocket science.

  1. Make note (take pictures) of which way the wire is wound on the core.
  2. Unwind the wire from the coil.
  3. Count how many windings are on the core.
  4. Measure the diameter of the wire.
  5. Measure the length of the wire.
  6. Order a roll of enameled magenet wire of the measured diameter that is longer than the wire you took off of the coil.
  7. Wind the new wire on the existing core in the same way as the original wire.
  8. Wind the wire neatly, with each turn lying next to the one before.

It will be a lot of work. You can expect to spend hours unwinding and rewinding the coil.

I took a closer look at the coil. It seems the wire may have been cut when trying to remove the insulating tape around the coil.

enter image description here

Both red lines mark places where the wires may be cut. I'm not completely sure about the lower line - that may be the cut edge of the tape. The upper line definitely goes into the wire, though.

JRE
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  • The other answers have excellent advice on what to check, the parameters to match, and the use of a cheap manual coil winder.

    Having said that, I'm keen on electric clocks, and have wound many a replacement coil (mainly voltage change, not due to failure). For instance I've just rewound four slave movements to 5V operation for use with USB PSUs instead of 12V or 24V supplies.

    Contact me via IM and I'm sure we can sort something out.

     – colintd Aug 22 '23 at 15:03
  • Those windings do look damaged: the wine-coloured enamel insulation on that copper wire looks corrupted by a sharp instrument (you have a good eye, JRE). Seems to be a simple coil having two ends. However, it may be powered with line-voltage AC, requiring some care regarding insulation. A similar International Time Recorder clock,USA https://i.ebayimg.com/images/g/oTsAAOSwilpk1~e~/s-l1600.jpg has two coils of different form-factor. – glen_geek Aug 22 '23 at 15:05
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You can get a manual coil winder for <= £40 from eBay etc., then sell it on, e.g., eBay, to get most of your money back. Do make sure that it can count the turns as you unwind the broken one, as you need to match that number when winding new wire on.

Andrew Morton
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It is probably not economical for you or companies to make a one-off coil, so I would suggest buying a new one at a supplier such as https://www.farnell.com/. If that is not an option, you can check the nearest technical university to see if some student or lab will do it for you, they should have the necessary equipment.

Torstein
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I can probably put you in contact with someone in the UK who can help.
But, see the comment that I will post re a possibly good place to ask.

You or a keen amateur could do this yourself. Wind off the wire using an electric drill or other small motor.
note the length AND you can provide a means of counting turns or do it manually (!).
Or you could take off say 10 turns and note the length of wire and do it several times as unwinding progresses and use this to get the mean turns. (Needs a little figuring).

Measure wire diameter with a micrometer and find suitable gauge for rewinding. If there is interwinding insulation it needs to be replicated. also note how layers were added - probably left to right then right to left then ... . You get maximum voltage between turns at the ends of each winding.

If this is mains powered then it's probably wiser to find a keen amatur.

As long a the new coil fits in the space available it can be "fatter". The wire diameter does not need to be absolutely the same but should be as similar as possible.

There is lettering on the coil and manufacturer's details on the metalwork Can you provide those. Is the coil operated at mains voltage or ...?

Russell McMahon
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