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Author Topic: Need help identifying TOKO coils  (Read 19110 times)

Posts: 57

« on: August 07, 2012, 12:28:49 AM »


I got a number of surplus toko coils. I tried to google for datasheets but no luck. Can anyone help me out or point me in the right direction?

These are the coils I have:

Code            Color   Shape
----            -----   -------
99501   52424   red      square
99501   82481   red      square
99501   82413   red      square
28071   83472   orange   square
27381   32072   red      square
28361   46wh   black      square
94ac   7a121   green   square
94fc   8a07sz   green   square
28291   46xc   yellow   square
28291   46wj   yellow   square
b0292   af622m   red   square
28291   15yp   yellow   square
53351         red   round
95673         yellow   round
95672         yellow   round
23841         orange   round
77402         yellow   round
76122         blue   round
bo353         green   round
158            black   round

Some have 1 number, some have 2 numbers printed on it. These are listed under code. A picture can be found here:

Thanks for your help,


Posts: 2087

« Reply #1 on: August 07, 2012, 11:58:06 AM »

well, one thing you could do is use them with a mica cap and a fet to make an oscillator, which yields the frequency in a counter window... which with a little math yields the current inductance... which placed with picture against a Toko catalog, gets an approximate equivalent part number.  they can't ALL be custom winds, right?

or just label with the inductance and put 'em in the parts pile.

Posts: 17483

« Reply #2 on: August 07, 2012, 12:59:32 PM »

Quote from: KD0REQ

or just label with the inductance and put 'em in the parts pile.

That's what I do.  Especially if they have been removed from equipment, because a lot of
such coils are custom-wound for a specific product, and are marked with the
manufacturer's house number.

I use an FET Colpitts oscillator designed for about 100pf effective across the inductor,
measure the resonant frequency range as the core is adjusted, calculate the inductance
from that, and mark it on the side of the can with a felt tip marker.  This has an advantage
over some inductance meters that operate at low frequency, as the core performance
can vary with frequency.

There are three common construction methods for canned coils such as these:  the "cup"
core (the top of the core takes up most of the top of the can), the standard core (a smaller
core down the middle of a coil on a small former), and a VHF style where the turns are easy
to count if you remove the can, the core is often aluminum (or missing), and the color of
the insulating plastic former may be used to identify values in different coil families.

The "cup" cores often have inductances around 700uH for 455kHz IF transformers with
secondary windings and an internal capacitor.  Red cores may have lower inductance
and no secondary winding and no capacitor - these are for the local oscillator.  Interstage
transformers are often color coded by application, but the color codes aren't universal
(especially for custom products.)  It is worth checking, however.

The small standard cores are often 10.7 MHz IF transformers, typically with a powdered
iron core rather than ferrite, and are more suitable for HF work.

VHF coils rarely have secondary windings, and usually have just two pins on opposite corners.

Here is a link that shows some coil types and rewinding recommendations:

I would say that his type A coil is typical of a 455 kHz IF transformer, and his type B coil
is a 10.7 MHz IF transformer.

The 10.7 MHz transformers and coils can be used on 40m and 80m simply by adding some
capacitance across the coil.  I've also rewound the 455kHz coils for 80m (it only takes 20
turns or less on the ferrite) but find that they aren't as stable for VFOs.  In some cases
there is enough frequency shift due to the effect of the Earth's magnetic field that one
can hear the pitch of a CW signal change as the antenna is rotated.

Posts: 4464

« Reply #3 on: August 07, 2012, 01:49:45 PM »

As a rule of thumb... The transformers on the top row with a RED slug will probably be the oscillator coil for a standard BCB AM radio. YELLOW core is likely a 455 kHz IF transformer, BLACK core will tend to be a 10.7 MHz IF transformer. Green or blue could be something like a ratio detector or 38 kHz FM multiplex oscillator. I rarely see those.

This web page mostly agrees with me, so it's a damn good web page:

The second row are more likely to be adjustable inductors rather than transformers. Your Ohmmeter can tell you how many pins have continuity.

Aside from that, they are mystery parts unless you can reference the numbers on the TOKO web site........................  Tongue


The end of the world will occur on April 23, 2018 ( the day after Earth Day. Go Figure ).  If you're reading this on April 24th look for updates coming soon.  If you're reading this after June first, fuhgedaboudit.....

Posts: 3160

« Reply #4 on: August 07, 2012, 03:24:05 PM »

TOKO (Japan) use to have good catalog listings of their Thru Hole coils.

Some TOKO distributors, such as UK distributor: BEC may have old catalogs / data sheets.

TOKO moved to surface mount products and discontinued many thru-hole products -- when RoHS compliance was required about 10 years ago.

Rewinding Toko 10K coils by Dave Powis, G4HUP

Rewinding by Dave Smith, G4COE

Rewinding Toko style coils

"L" meter

« Last Edit: August 07, 2012, 03:38:20 PM by W9GB » Logged
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