hand winding a crossover coil?

Thread Starter

neospam

Joined Jan 13, 2020
103
I have a old set of cerwin vega 317P that I am going through. I am having a hard time finding a replacement inductor for a coil that is burned out.

Iron core 0.40 mH, @ 1.6 ohms.. the wire is around 30 awg. - hard to find

Few questions never wound anything but a magnet.

What can I use for Iron core? It looks like the old core was a ferric metal, magnet?

How hard is it to wind? Do I need to use cross hatch patterns coming back over the existing run or a parallel type winding?

thanks.. hope everyone is safe
 

KeithWalker

Joined Jul 10, 2017
1,132
Is there enough of the burned out inductor left to get a close idea of how many turns of wire it had on it? If it is badly damaged, count the layers and estimate how many turns should be on each layer. If you can figure that out, you can use the same number of turns on the old ferrite core using the closest thicker gauge of wire that you can get. The inductance doesn't have to be exact - just as close to the original as you can get it. Just make the turns parallel in neat layers. Use a few spots of crazy glue to hold the wire in place as you are winding it. It really doesn't matter if yours has more layers because you are using thicker wire. This is the inductor that is in series with the bass speaker so the thicker wire will give you a bit of extra protection against another burnout.
Regards.
Keith
 

Thread Starter

neospam

Joined Jan 13, 2020
103
Jantzen is about the only company that I could find close and those were all overseas UK. Right now not sure how that's going, emailed a company some weeks back. Looking at plan B or C

The speakers that I am going through. I am original owner and I purchased these when I was a teen (40yrs ago). 1-coil burned out, long story short - was replaced with non-matching coil and I do not have the original. I do have the other speaker and that's still original. I was given a iron core inductor that was not close.

Do I know if they are in series, no don't. But 99% w/o checking they are not in series with woofer. I do think the design considers the power requirements. There is a resistor on the back of the mid-potentiometer, I have look at that later on how its wired. Finding a inductor/coil is not easy.

What would you use for ferris core, those are magnetized?
 

KeithWalker

Joined Jul 10, 2017
1,132
Ferrite material used as cores for inductors have very different frequency and saturation characteristics. If you are going to wind one from scratch, make it air cored unless you are sure that the ferrite core that you have is right for this application and you have the specs of it to let you calculate how many turns to use. There are calculators online that will help you choose the dimensions of an air cored inductor with the wire you have available.
I have done it a number of times. Once you know the dimensions, make a rolled paper tube over a piece of dowell, or use a plastic tube if you have one the right size. Make a pair of circular cardboard or plywood end pieces. Make a hole through the middle of the dowell and end pieces and put a machine screw through them, gluing the end pieces in position to make a bobbin. Add a washer and nut and tighten it up. Mount the screw in the chuck of a mechanical hand drill (not electric!) and mount the drill in your vice. You can then feed the wire onto the bobbin in neat layers as you turn the drill handle. Tape each layer in place with mylar (invisible) scotch tape.
When yo have finished, remember to take the screw out of the bobbin. You can mount the inductor in the speaker using a nylon screw through the center hole.
Have fun.
Keith.
 

Thread Starter

neospam

Joined Jan 13, 2020
103
Ferrite material used as cores for inductors have very different frequency and saturation characteristics. If you are going to wind one from scratch, make it air cored unless you are sure that the ferrite core that you have is right for this application and you have the specs of it to let you calculate how many turns to use. There are calculators online that will help you choose the dimensions of an air cored inductor with the wire you have available.
I have done it a number of times. Once you know the dimensions, make a rolled paper tube over a piece of dowell, or use a plastic tube if you have one the right size. Make a pair of circular cardboard or plywood end pieces. Make a hole through the middle of the dowell and end pieces and put a machine screw through them, gluing the end pieces in position to make a bobbin. Add a washer and nut and tighten it up. Mount the screw in the chuck of a mechanical hand drill (not electric!) and mount the drill in your vice. You can then feed the wire onto the bobbin in neat layers as you turn the drill handle. Tape each layer in place with mylar (invisible) scotch tape.
When yo have finished, remember to take the screw out of the bobbin. You can mount the inductor in the speaker using a nylon screw through the center hole.
Have fun.
Keith.
Thanks for help, sorry for so long getting back. I am still working this out. I am going through a pair of cerwin vega 317P (orginal owner), and rebuilding the crossover. The crossover I am rebuilding or replacing parts. 1 coil for High freq I replaced a few decades ago with the wrong inductor. I cannot find a replacement, and plan on winding one to see how it does. If I get the henerys right and resistance I should be closer then were I am. The original tweeter cross got burned out, and never had the right part. I am rebuilding, refinishing, reforming, the speaker and reworking the crossover.

Right now my ferrite cores are on back order from digkey until about july. Bought 2, just in case I want to wind a 2nd.
This is on going project, started last fall. I hope to get them back together this summer... will see
 
Top