Nihon Kohden Output Transformer

[CJ]

Full props to radeng for sending this down the line for "analysis",

this guy is from Japan, Number 1-427-603-11 TKOH is written on the cover, which probably stands for Toyoko.

Sony has used these as audio output transformers,
has a 180 and 37.5 Ohm primary and three secondaries at 37.5 ohms each.

it measures very well.

and is very hard to photograph>

 

[CJ]

primary inductance on the 180 ohm primary is

23 Henrys at 20 Hz and 2 volts rms input voltage.
and
9.7 Henrys at 100 Hz.

plenty of juice to run as a line input

it can take 5 V-rms on the pri with no distortion.

here are some sq wave shots to check ringing>

 

[CJ]

sawtooth wave at 100 KC,

superimposed pri-sec traces at 100 KC (no phase shift or signal peak/loss) and 1 M Hz>

pretty darn good xfmr, wondering how it is wound, could be bi-fi,

will open it up tomorrow,

 

[CJ]

grind down a corner on the belt sander>

 

[CJ]

open the mu can up like a can of Brunswick sardines,

 

[CJ]

out pops the transformer after we clip the leads, double sided tape on the bottom, Nomex insulation which means top quality>

 

[CJ]

lots of splices,

 

[CJ]

cool lams,

 

[moamps]

Thank you very much for this thread. I have a lot of these transformers, Sony used them as line splitters. Most likely they are actually Tamura transformers. I'm wondering if you're going to take it apart completely.

 

[CJ]

gonna try,

check out theses 16 screen leads, wtf?

nightmare to wind,

 

[Script]

Nihon Kohden was founded in 1951. Stock listed today. It is provider of high-performance medical equipment. They have their own factories, so it's likely they wound their own transformers

 

[CJ]

They sold their XFMR division a while back,

 

[Tubetec]

So if theres 16 interwinding screens in total 8 on each bobbin , thats a lot of sections , each carefully balanced and even a 1Mhz sine gets through without being mangled beyond all recognition , thats impressive .
Looking forward to seeing the winding sheet for this , as we can see its not just fairy dust and marketing bluff that makes these and other Japan made transformers superb performers .

 

[CJ]

This guy has 3 primaries on each coil all wired in parallel.

There are two secondaries on each coil. Each secondary has two equal sections.

There are 6 shields per coil. Not 8.

So the structure is
1/2 sec A - pri - 1/2 sec A - pri - 1/2 sec B - pri - 1/2 sec B

With screens between each section.
There is no layer insulation but the turns lay flat with no cross-overs which is pretty amazing.

There are 737 turns in each primary section of #36 and 220 + 220 = 440 turns of #33 in each secondary.
Note that the wire is probably metric since this XFMR is from Japan.

So the impedance ratio stamped on the cover is an approximation.

180 ohms to 37.5 ohms translates to a Z ratio of 4.8 to 1.

This translates to a voltage ratio of 2.19 to 1.

The turns ratio is 737 to 440= 1.675 to 1.

The cover plate shows one secondary on the primary side, they probably ran out of room on the secondary side.

The laminations are unbelievably unique like nothing I have ever seen before. Will post pics and blueprint when I get back to work.

 

[radeng]

Thank you very much for this thread. I have a lot of these transformers, Sony used them as line splitters. Most likely they are actually Tamura transformers. I'm wondering if you're going to take it apart completely.

I have a number of these too, besides the one CJ has taken apart. Now that you have seen the specs from his excellent report, what are your thoughts as to possible uses beyond line splitting?

 

[ruffrecords]

What is the core cross section area and the core material?

Cheers

Ian

 

[CJ]

here go the lams, there are 76 of them, 0.0135" thick, with a stack height of 0.536"

they have to be stacked in a certain way otherwise you get a crooked window, (right pic)>



alternate stacking gives a look like this>

 

[moamps]

I have a number of these too, besides the one CJ has taken apart. Now that you have seen the specs from his excellent report, what are your thoughts as to possible uses beyond line splitting?

These transformers can be used in any position where the source is low-impedance as line output transformers, but would certainly be the best position as output transformers in an active microphone splitter.

@Script
Nihon Kohden obviously has some strong connection with Tamura. I haven't researched it in depth. At Japanese auctions, they are almost always advertised as Tamura, and some transformer models look identical to both companies.

 

[CJ]

print>

 

[radeng]

These transformers can be used in any position where the source is low-impedance as line output transformers, but would certainly be the best position as output transformers in an active microphone splitter.

Would a mic splitter using these have to be active? I do have some mics (old RCA ribbons) that can be strapped for different output impedances, including 50 ohms. I have built mic splitters using the Jensen JE-MB-D's, could these be used in a similar manner?