Jukebox relay coil rewind?

[AndyPen1981]

Hello everyone new member here, I am in need of some help and information regarding a jukebox relay coil.

The relay is from a chantal meteor jukebox and appears to be burned out as is isn't acutating when provided with the correct voltage or when the circuit is activated via the jukebox.

Taking a reading from the coil gives a 1.7k ohm measurement but as there are two other coil operated devices that work connected to the power input of the faulty realy coil ,  the reading will not be of the coil in question please see pictures.

The coil on the relay is a 240v AC coil with two contacts, my question:

1. Is it possible to rewind the coil as a DIY job at home myself?

2. What calculations are required to achieve the correct amount of turns etc.. or is there more simpler way of doing things?

3. Do the number written on the coil/relay body  give the ohms that the coil is supposed to be. See pics.

I'm not an expert in electronics or have much experience but I do like to have a go at things, I know I can replace the relay with a modern unit and have bought the correct relay for the job, but I'd like to if possible have a go at fixing the original one.

Hope someone can help.
Many thanks Andy

[Doctorandus_P]

Is that a coil with a single screw in the center of the bottom?
If that is so, you can easily take it apart, take some other screw and put it in a drill chuck and screw the bobbin on that.

I do not have much experience doing this, but it seems logical that the number of turns (especially for DC) is not very critical.
I'll explain:

Let's assume you're grossly out, and put 2 times as many turns on it as you should.
Then the DC resistance will also be approx twice as the old coil. (outer windings are longer).
This results in half the current through the relay.
Each winding will attribute only half to the magnetic field, because of the lower current through the wire.
But you have twice as many windings, so the total magnetic field will still be the same.
You've just built a more efficient relay which needs less power to activate it.

For (old?) reed contacts, you can sometimes find specs for AW = Amps * Windings which is needed to activate it.

This of course only holds true if you use exactly the same wire thickness.
A 230V coil will have very fine wire, which is difficult to handle manually without breaking.

My guess is you'll be better off with replacing the whole relay, unless the steampunk looks are important.
Buying just some loose wire is probably more expensive then a new relay.


Edit:
Oops, with AC it's different.
Twice the number of windings, will result in twice the inductance of the coil.
Whether this is a problem depends on how much of the impedance is from the resistance, and how much is from the inductance.

If you can only source thicker wire, then the voltage for the coil will be less to activte it. (Thicker wire is less Ohms for a meter of wire, and also fewer windings for the same mass of copper). In such a case, fit as many wire as will fit, and use a series resistor (or capacitor for AC) to make up the difference.
For AC it may be good to add a resistor to limit the Q- factor and risk of oscillations.

[Seekonk]

It doesn't appear to activate anything else mechanically. Just replace it with almost anything DPDT. Make sire it is hefty as those contacts have a little burning rom heavy use.  Is one welded? That might explain the relay armature not closing and the coil burning up.

[james_s]

1.7k sounds about right for a 240V coil. Does it buzz when power is applied? Are you sure the relay isn't mechanically jammed? Are you sure it's getting power?

Rewinding a coil like that is really not hard at all, it's just a matter of getting a spool of the same diameter magnet wire and then either calculate or count the turns as you unwind it and wind a new one. If it actually burned out though the bobbin may be melted.

[AndyPen1981]

Thanks for all the replies

I think I have found a company that will rewind the coil for me, just waiting for confirmation now.

I do have the correct modern coil for the job but I just wanted to know the possibility of doing the rewind as a bit if a DIY project

Many that is for the help.

[james_s]

I would not hesitate to DIY it, but it all depends on how handy you are. The coil is nothing more than a few hundred turns of wire on a plastic bobbin with some tape over the top layer. The only tricky bit is that especially for 240V the wire is going to be extremely thin which makes it easy to snap if you're not careful and then you have to pull it all off and start over with a fresh piece.

I'd imagine there must be specialty companies that can supply new coils for vintage stuff too, I know they exist for pinball machines.

[TheMG]

A 240VAC relay coil is going to have A LOT (on the order of thousands) of turns of hair-thin wire. You could DIY rewind but it's going to be a long and tedious process, and a very delicate one too as the small wire can break easily.

This is a job best done with a coil winding machine. I would either replace the relay or if maintaining the original appearance is important, get a pro to do the re-wind as they would have access to such a machine.

[james_s]

That's a good point, it's going to be extremely thin wire.

It's possible that there is a modern relay that has a coil of the same form factor so that's another option.

[Seekonk]

Not that old clunker. who in their right mind would make such a thing today.

[james_s]

Not that old clunker. who in their right mind would make such a thing today.

Not the whole thing, the coil. A lot of modern (and not quite as ancient) relays and contactors have very similar looking coils. Whether one has a similar enough coil to be a drop in replacement I don't know.

[WattsThat]

Welcome! No, the writings on the device don’t provide any useful information. To rewind, match the wire gauge and wind to the same amount of fill. That’s close enough because if the coil has failed, it will be a big burned mess and the wire will break trying to unwind and count turns.

Please allow me to provide some free advice. Relays are electromechanical devices. They spend their lives banging their contacts together. It’s more likely to be mechanically bound or suffer from pitted contacts than an open coil. Failed coils usual bake until the wire insulation fails so there is usually evidence of overheating. I see none in your photo. What to do? TEST IT!

Without power applied, force the relay closed, a finger tip is all all you need. Push in the right place and the contacts will close. Then you measure the contact resistances, might take two people or clips on your meter, hard two hold two probes and operate the relay unless you have three hands. If the contacts are good, measure the coil resistance. How?

With an appropriate knife for your skills, cut the heat shrink off both of the terminals. Unsolder the single wire terminal. Measure the resistance of the coil. It will either be open or okay at 2-3000 ohms since the typical current of those relays is 50-100ma.

Let’s us know what you find. We like happy endings.

BTW: is it the lighting or is the far contact on that relay stuck? I don’t see any daylight through the contact as you can with the one in the foreground. It sure looks like the far contact is welded together to me... the spacing of the contact arms is definitely different.