If you go down far enough they actually have a 6H inductor, but it will not fit well mechanically.

 

Also My friend Steve and I estimated the length of wire about 18 feet.

Aram

Using all the numbers you gave me with a toroidal coil formula gives me 2.4 H. This is close enough to indicate that the 6H number is probably correct.

 

Figure around ¾" per turn, 18 feet works out to 288 turns. Maybe, but seems a bit short on the turns.

Still, didn't know that you could get such small sizes for large inductors.

 

Also My friend Steve and I estimated the length of wire about 18 feet.

36awg copper is about 1.4ohm / m, so 100ohm equates to about 70 meters, or 210ft. try to fit that much wire to a tiny core.

 

At that size I wouldn't assume a specific gauge. It could be even smaller wire. Given the large inductance in a small space, entirely likely.

 

Okay... I freely give in on the 18ft. Steve and I both had sandwiches in our mouths and get interrupted quite a bit, But this mystery still remains. I measured the DC resistance of the good one in circuit and got 100 ohms. I also have a LC77 analyzer and it also said 100 ohms (not Z).

Sorry for the lousy pic. I still haven't mastered the Camera on my Blackberry yet. Ill try to use my sony camera and take a nice detailed pic this evening.

Aram

 

Would anyone care to comment what the ur might be for a sintered toroid core built 30 years ago?

Aram

 

is it a toroid or just a multi-layer cylinder inductor? i ask because all of the online toroid calculators show roughly the same answer of needing 5600 turns on a ferrite core for 6H.

 

If you chose a pot-core instead of a toroid you will experience a lot less grief winding the inductor.

hgmjr

 

If you chose a pot-core instead of a toroid you will experience a lot less grief winding the inductor.

hgmjr

i'm just trying to figure how this mystery inductor is a 6H toroid with just 18ft of wire on it.

 

It's not that hard to get 6 H in a small package. You just have to use high permeability core material, like permalloy dust.

I've attached a photo of some inductors from my junk box, with their measured inductances.

The one on the far right is probably made by the same manufacturer as the one you have. I happen to know that it was made by Victory Engineering (VECO). I can't find them on the web; their site seems to be down.

Also, El-Rad is out of business.

However, here is a source for inductors like the 1.38 axial leaded unit in the picture: http://www.rencousa.com/static/products/inductors/1123.html

Notice they've got units up to 47H.

The resistance of their units is not as low as the one you have. If you have the room on the board you could series-parallel several to increase the effective Q.

 

Thank you Electrician...and other folks...

As promised, Here is a better photograph of the inductor. I can't believe there is more that 20 feet of wire on this thing, and certainly not 200 or 1000.... which still is a mystery... But math doesn't lie, so if we can pretty accurately guestimate the core size, and we the resistance and inductance.. It shouldn't be to hard to calculate the wire length.

So I turned to my HP calculator and ran the toroid equation.

ur=5000 (relative permeability)
N=Solving for this
h= approx. 3mm (toroid thickness)
ri= approx 5mm (inside radius
ro= approx. 13mm (radius outside)
L= 6 henry

N burped out= 1446 turns (Eehhh i doubt that)

Okay so How much does one turn equal in length?

Lenth for one turn= 3mm+3mm+4mm+4mm=14mm for one turn.

So 1446 turns X 14 mm= 20254 mm long (length of wire on core)

In feet= 66.45 ft... (gee that seems like a lot)

What kind of magical machine can wind this thin wire on a loop without breaking it??? Wow


Take a look at the photo, zoom in and tell me what you think???

Aram

PS I'll follow the inductor sources posted here.. I may have some luck getting close. The exact resistance may pose a problem though.

 

in 1971 i suspect winding machines were progressing some, so its very likely a winding machine made it.

lets consider 100 ohms(dc) as accurate, so that wire must be in the 43awg range. 42awg and 43awg are common size for guitar pickups.

36awg 100ohms(dc) = 241ft
37awg 100ohms(dc) = 191ft
38awg 100ohms(dc) = 151ft
39awg 100ohms(dc) = 120ft
40awg 100ohms(dc) = 95ft
41awg 100ohms(dc) = 75.5ft
42awg 100ohms(dc) = 60.2ft
43awg 100ohms(dc) = 46.6ft
44awg 100ohms(dc) = 38.56ft
45awg 100ohms(dc) = 29.8ft
46awg 100ohms(dc) = 23.7ft
47awg 100ohms(dc) = 18.8ft
48awg 100ohms(dc) = 14.8ft

also, you said you unraveled one and it was just 18ft long, and your calculation yielded ~66ft. so, its either 42awg (common in guitar pickups), or 47awg.

having a calculation of ~66ft and a physical unwinding of 18ft is somewhat confusing. did you measure the dc ohms before you unwound it, or was the 100 ohms measured on the intact one?

also, to see if its possible with just 18ft, run through the equation using 18ft of wire, perhaps solve for ur, maybe they were using special nasa materials in 1971. you never know, wd40 slipped out. perhaps the core is from roswell

 

Indeed they are commercially available.....looky here----->http://www.picoelectronics.com/plugin/pe57_59.htm


These are pot core inductors....probably wound with 64 ga wire!

Eric

 

Indeed they are commercially available.....looky here----->http://www.picoelectronics.com/plugin/pe57_59.htm


These are pot core inductors....probably wound with 64 ga wire!

Eric

their ~6H coils have ohms in the 1,000's
i guess the dc ohms can be brought down with a parallel resistor. not clear to me if the OP is looking for a direct replacement, or just a 6H coil.

 

Sorry DC:

My fault for not being clear... No I have not unwound it, I made a rough estimated calc, which is obviously wrong.

The latter calcs are more accurate based on electrical and estimated mechanical measurements.

Yes I'll take an original or find anything I can make fit, so long it doesn't throw the Q off too bad.

Renco... doesn't look like it will pan out either after talking to their engineer. They do qty only.

Wow I wasn't aware that guitar PU's were 43 awg.. Actually how small can you draw copper wire???

Aram

 

Okay... So can anyone suggest any options here?

Maybe I can Spool one on a cordless drill????

Aram

 

Renco... doesn't look like it will pan out either after talking to their engineer. They do qty only.

Wow I wasn't aware that guitar PU's were 43 awg.. Actually how small can you draw copper wire???

Aram

What you might try is pleading with the Renco guy. Tell him you only need one and could he please send you a sample. Also, ask him if there are any distributors who stock their stuff.

I have a roll of 51 gauge wire, and it's enameled! If you break off 6 inches and drop it, it practically floats on the air. Don't ask me how they draw it that fine.

I did a simulation of the circuit, and it appears that if your resistance is 500 ohms rather than 100 ohms, you will lose some boost and cut at the extremes, but the effect isn't much at less than full boost and cut.

I've attached a couple of images showing the boost and cut with 100 ohms and with 500 ohms, at full boost and cut, and at somewhat less.

Since the user will adjust the boost or cut to suit his ear, unless he really needs that extra 2 dB at max or min, he will just turn the knob until he likes what he hears.

 

Sorry DC:

My fault for not being clear... No I have not unwound it, I made a rough estimated calc, which is obviously wrong.

T

Since you haven't unwound it, there's a possibility you could repair it. If the break is near the terminals, you could carefully cut away the urethane, and maybe fix it.

The problem is going to be finding out where the break is. What I would do is get a transformer that could put out 2000 volts. Energize the primary with a variac, put a 330k resistor in series with the 2000 volts and apply this to your inductor. Be in a dark room, turn up the variac and look for the tiny spark where the break is. If you're lucky, it will be where you can get at it.

Seems a little drastic, buy you've got nothing to lose!

 

If all else fails, and you're really desperate to get this equipment going again you could wire up an opamp based inductor simulator on a piece of vector board and kluge it in there.

You could tap off some available voltage, use a TO-92 voltage regulator (or two of them if you've got a negative supply available) with almost any old suitable opamp; it's only 50 Hz where the action takes place. You'll have to make sure the simulated inductor continues to look like an inductor up to the top of the audio band.