Unknown coil

[ElectronicRider]

Does anyone know where to get this coil?

He has 4 pins and looks like an isolator with 3T:2T or something like that (Coil: T1)

[radiolistener]

this is hand made transformer on Amidon toroid core, according to the color of the toroid, probably the core material #2 (red color, µ=10, see Amidon documentaton)

[ElectronicRider]

Oh handmade, good to know :-) 

Is there a store to buy one similar?
Or do I have to create this myself too. The question is how to do it, with what wire and what core (ferrite or iron).

[vu2nan]

Hi ElectronicRider,

It's a toroidal output transformer of an RF oscillator / amplifier in a 'Donkey Kong Nintendo' video game.

https://www.arcade-museum.com/manuals-videogames/D/dk-tkg4u.pdf (see page 32).

The crystal frequency is shown as 61.44 MHz in the schematic. It's must be an overtone crystal, but it's not clear whether the oscillator is for one-third or one-fifth of the marked frequency.

It should be possible to wind the transformer using a HF / VHF toroid.

Nandu.

[radiolistener]

yes, you can do it, this is easy. These toroid cores from iron powder, you can buy them. But note, these Amidon clones on aliexpress a little worse than original and have more high loss.

You're needs to know toroid size and material, at a glance it looks like material is #2, which is used from 1 to 15 MHz. But I'm not sure, the color of core is not clean on the photo. And I see that there is a crystal resonator for 61 MHz, so may be there is another material.

I think material #6 will be better for 61 MHz. Or may be there is a sense to use material #12, but I never used this material.

If you have original transformer, check it's core color code to understand what kind of material is used.

[RoGeorge]

The most important is to have a magnetic core good enough for the frequency of the circuit (probably ~60MHz from the X1 Quartz shown in the schematic), and to keep the same ratio between its primary and secondary coils.

The wire is normal CuEm isolated, the number of turns can be spotted from the picture.  Same for the wire diameter, compare it in the picture with the width of a resistor's terminal, the exact diameter is not critical.

Can be easily hand made, something like this:  https://youtu.be/sDIWNHOoNh8

[ElectronicRider]

Many thanks to all. Very good information and exactly what I needed. I will try it with a T50-10 and 0.5 mm 8:16 turns.

[Paul Rose]

If you are just buying a few (not in bulk), and are in the US, I've had really good luck with the small shop https://kitsandparts.com for buying both powdered iron and ferrite toroid cores for RF projects.