Are you trying to wind this on that torrid? Really fine wire, a good magnifying headpiece, a little superglue now and again, and really tight loops with no spaces between them are your friend.

That or buy one of the smaller of the units we referred to earlier, and adjust the resistance with an external to match. Start with 6H, and go from there. Is your heart set on DIY?

Even on an open bobbin my 1st paragraph applies, but I am under the impression a torrid increases the apparent inductance in a small space.

 

More like "DIN" do it now... I think I have to throw in the towel... I couldn't find a 6 henry with 100 ohms or less resistance that is reasonably sized unless you know of a source.

Aram

 

I have an inductance meter, but I have already posted a pic of the mystery inductor... What else do you need to know?

Aram

yes, i'd like to see in on the meter.

 

Why not do a circuit simulation?

 

Circuit simulations aren't reality, sometimes they aren't even close. If you read the whole thread he's needing this to do a real world repair.

 

I do not agree. By doing a simulation, we could confirm if the value needed is 6H or something else.

 

Again, this is a replacement part, not a new design. That work has been done, and if you read the thread you will see where people have simulated what the part does. Being a stereo amplifier, it is a bit important that the two sides match fairly closely.

 

I found this forum. You have perhaps allready been there, but in case not

http://unofficialacousticcontrolcorpmessageboard.yuku.com/topic/2179/t/EQ-Chokes.html
Perhaps the people there can help you out

 

The inductor is on the slider of a 50K pot.

It's DC resistance will only have any significant effect at the limits of the pot. adjustment.

Get any 6H choke (up to 600 Ohm DC resistance) small enough to fit in the equipment and wire in place, then IF you find a problem with the control range, adjust the fixed resistors at the ends of the pot to bring the minimum resistance back to the original.
eg. If the choke resistance is 300 Ohms higher, reduce the end resistors by around 300 Ohms each.

 

Perhaps this firm can help you out. I guess it depends on how much your customer are willing to pay and wait. Since the L102 is placed at the PCB outer edge you have some space to work with.
http://www.sowter.co.uk/eqinductors.php

 

Wow great find on the acoustic link. I had been there but did not see that issue. I looks like his inductor is "repairable" but mine is not. Apparently this is a common problem..

Bill just to clarify.. this unit is a Bass amplifier (for Bass guitar).

I guess I could register and see if someone has an inductor to spare...

Another pass word and username.. When will it stop!

Aram

 

My mistake. It stops when you have one? Good luck either way.

 

You'll never be able to rewind your existing toroid by hand with such fine wire.

In notice that the inductor in this post:
http://unofficialacousticcontrolcorpmessageboard.yuku.com/topic/2179/t/EQ-Chokes.html

is a pot core.

I have a small pot core I could send you, complete with bobbin. This bobbin could easily be wound by hand. You can put a dowel through the center hole and wedge it in, then spin the dowel with a variable speed drill.

My calculations indicate that about 1200 turns of wire (about 150 feet) would give you about 6H with less than 100 ohms DC resistance.

If you could do the winding very precisely, AWG 36 would probably do. But for a scramble wound version, you might have to use up to 40 gauge.

Theoretical DC resistances would be:

36 gauge---53 ohms
37 gauge---67 ohms
38 gauge---84 ohms
39 gauge---106 ohms
40 gauge---134 ohms

This pot core, while small, is still larger than what you've got, but I'm sure you could kluge it in.

If you're interested, post a valid email address, disguised with spaces or periods between characters.

 

If you get and old one, it is some risk that it will fail again after a short time. But this is actually up to your customer. If he want things to be 100% original. You get an old one. If he is happy with a new but not original part you may find a new here http://www.sowter.co.uk/eqifm.php

 

yes, i'd like to see in on the meter.

i too would like to see this...

 

Why not just get a 6H inductor, then add an external resistance to make it 100Ω. 2 components, much simplier.

This is not good advice. You will not achieve what you want!

Here is a plot of what happens to the effective inductance and series resistance when you place a 125Ω resistor across a 6H inductor that has 500Ω series resistance.

You can see that the resistance is around 100Ω as expected, but the inductance starts at around 0.24H and drops! So by placing a 125Ω resistor across your 6H/500Ω inductor you reduced the effective inductance to 0.24H!

If it was this easy, we could increase the Q of any inductor by simply adding a shunt resistor!

So the bottom line is that if you need this Q (and I haven't studied the circuit to see if you do) you need to lower the losses, using a shunt resistor will not work.

 

I did not say parallel, I said series, which would be identical. Black box electronics, if you have an ideal coil with a 100Ω resistor, or a coil with 100Ω in the windings, you could not tell the difference.

You're not the first to make the assumption though, I wonder why? It seems obvious to me.

 

I did not say parallel, I said series, which would be identical. Black box electronics, if you have an ideal coil with a 100Ω resistor, or a coil with 100Ω in the windings, you could not tell the difference.

Yes that is correct. If we shall be 100% so correct so will a resistor at some frequency stop acting like a ideal resistor. But for a low value resistor in the audio frequency range this is not imortant. It is futile to even disuss it.

 

Gentleman:

I feel like we are at a corporate meeting. I wish i could express how much I appreciate everyone's input for the inductor from hell.. Which is what this post should have been called..

DC, I am assuming you doubt how i am using the LC77 to measure the good inductor. I measured it's twin in circuit, and it jived with schematic, and I think we all agree by now that it truly is 6H. I am not sure why you want a pic of me measuring it again... Please explain what the goal is.

Otherwise gentleman, I don't think I have the patience to build one of these by hand, especially looking at the pics on the Acoustic enthusiast site. I guess I could talk to my client via to customer and see if they would be willing to pay more. If so, would someone be willing to try? I think the easiest thing to do is make one on a standard core, then series a resistor, and bend the two in half making it radial like. I could shove that in the PCB.

Perhaps $20 bucks and maybe a coupon for a bowl of soup or a Dr. Scholls pad or something might entice someone.

Aram

 

I did not say parallel, I said series, which would be identical. Black box electronics, if you have an ideal coil with a 100Ω resistor, or a coil with 100Ω in the windings, you could not tell the difference.

You're not the first to make the assumption though, I wonder why? It seems obvious to me.

Ah I see the problem - my apologies. However, in the context of the thread where the main substitutes under discussion had r ≈ 500Ω and his coil had r ≈ 100Ω, your suggestion as phrased was easily misinterpreted. This exchange didn't help:

What is to be done if the 6 H inductor already has 500 ohms resistance?

You can try it, but I don't think it is usable that way (it would probably work pretty closely though). I was thinking of a lower ohmage part, I saw several during my search.