Calling old inductor experts.

[digi2t]

Picked up a Conn Multi-vider the other day. Opened it up, seemed to have suffered from humidity damage. Cleaned it up somewhat, and started testing components, and I found that the inductor was kaput. The varnish had deteriorated to the point that the connection points between the pins and the core had been broken. I couldn't even get a resistance or inductance reading. I have a picture of it, it shows a "5H" marking. I'm wondering it means 5 Henries, or if it's company code for some other specification.

Anyone happen to know anything about these inductors?



I'll try and get the complete schematic up soon.

[waltk]

When I saw the post title, I thought - is he looking for old-inductor experts or old inductor-experts.  Unfortunately, just plain old doesn't qualify, so you'll have wait for the real answer.

I'm guessing you would need something a bit bigger than that to get 5H inductance.

[Mark Hammer]

Umm, they're delicious chocolate treats?

[digi2t]

Umm, they're delicious chocolate treats?

When I saw the post title, I thought - is he looking for old-inductor experts or old inductor-experts.  Unfortunately, just plain old doesn't qualify, so you'll have wait for the real answer.

I'm guessing you would need something a bit bigger than that to get 5H inductance.

That may be true. The Honey Special Fuzz used two TDK 4 Henry inductors, which are a little bit bigger than this one. I might end up having to try several different models, trial and error style. Just thought is some guru might have seen this in their travels, they might throw me a bone. Maybe I'll hit up Joe Gagan for a look-see.

[thermionix]

I agree it's small, but could be wound with very fine wire, and that could be partially why it's now open.  Since it's already fubar you could try to get in and have a look at the windings.  If it looks like pickup wire, maybe it is was 5 Henrys.  Maybe a pickup builder can rewind it for you.

[digi2t]

I agree it's small, but could be wound with very fine wire, and that could be partially why it's now open.  Since it's already fubar you could try to get in and have a look at the windings.  If it looks like pickup wire, maybe it is was 5 Henrys.  Maybe a pickup builder can rewind it for you.

I did open it up, and yes, the wire is EXTREMELY fine. I've seen some fine wire in my time, but this is measuring in at 0.0015 inch, or 0.04 mm, which charts as 46 or 46.5 gauge. Unfortuneatly, the casing (ferrite?) broke when it came apart, so it's pretty well fubar now. I'll have to find something else to replace it. Right now, I'm waiting on some axial caps to replace the electros, so I'll concentrate on sketching out the schematic for now.

[Mark Hammer]

Are you trying to reverse engineer it?  I have the feeling that somebody over at MEF posted a link to a schematic or other technical info about it some years ago.  You might want to try there.

[R.G.]

In the absence of an other info, I'd guess at 5 henries, as you did.

It's not too hard to get to 5H with a pot core, as that appears to be, with pickup winding equipment. And it's even easier if you allow yourself to go to a bigger pot core. The inducti-ness of a core goes up as the area of the core inside the wire, and that scales up as the square of the linear dimension, so a pot core twice the diameter has four times the inductance per turn, all else being equal.

Inductance also scales up with the square of the turns. A 5H inductor has 2.23 times as many turns as a 1H inductor on the same core, and only 3.16 times as many turns as a 0.5H inductor on the same core, that being the value of our friend, the wah inductor.

Of course, wire area remains the same, so getting 3+ times the turns in the same area as a 1/2H inductor means the wire gets a lot finer, too.

It's not too difficult to estimate a core and turns for a given inductor on pot cores. I'd volunteer to do the guesstimating if you can provide more particulars. The rest of the circuit would give a good guess about whether 5H is right.

The Vox amps used an assortment of big inductors; 0.5, 1, 1.5 come to mind in different amps. The Thomas Vox amps everyone thinks of as "vox" in the use used 0.5H  for the "big head" series (Beatle , Guardsman, Buckingham, Viscount) and 1H in the smaller Cambridge and Berkeley. I have a Guardsman on the bench now.

I had to short the inductors to foil their hum pickup while I went hunting for the cause of the persistent hum.

Pesky inductor/pickups!

[petemoore]

 If / when I get the henry/cap measuring equipment, I'll measure the inductor henries of the coil I threw into my wah, which makes it wah as good as I remember [had a tdk, then y fasel, yfasel broken...but the 2.5''s of coil that it is makes excellent pickup also, introduces copious amounts of noise to the signal.
  I'll resist giving in [trying to find, fit or diy an inductor] until I give up and buy a replacement.

[digi2t]

Are you trying to reverse engineer it?  I have the feeling that somebody over at MEF posted a link to a schematic or other technical info about it some years ago.  You might want to try there.

Mark, could you elaborate on "MEF"?

I have found an older schematic for this, but it doesn't jive with what I have on the bench. I have a later version, that uses a 4013 chip.

EDIT: Nevermind on the MEF, I figured it out.   

[R.G.]

Ibedanged.

I found the schemo for the earlier Conn Multivider, and there, right at the input preamp, is an early version of the JFET Doubler.

There apparently isn't anything new under the sun. 

That's probably the cause for the octave up in the early one at least.