Prayudi's 12AF6 / LM386 Radio built in Indonesia.
My idea is a tube radio that I can play as an ordinary radio, so I made this 12AF6 AM tube radio with mini amplifier to drive audio. I am using a LM 386 circuit as audio amplifier and a power supply rather than battery as the power.
I started with make a pinewood box. I choose pinewood because the wood texture looks good and easy to work with.
I bought a sanded pinewood board and started my project on 17 May and finished on 22 May. But because my friend and I aren't craftsmen, the box we have made was not very good. It looks unsymmetrical. I didn't varnish it yet because I like the plain color of pinewood. I use FOX glue (a special glue for wood work) to make the box, except the front part I used screws so I can open it and install the parts.
First, I drilled some holes in the front cover part to mount the variable capacitor and speakers. The holes in the top for the tube socket, volume control, regeneration control, antenna ground plug-in, and coil part.
Wheuuh, it's a long weekend for us! But we finished it!
Then I mounted the power supply transformer and adapter circuit in the base. The socket, potentiometer, 12AF6 tube, and audio amplifier came later after I glued the box. To get the antique nuance I use a five-strip terminal to mount all electronics part of receiver, but I used a PCB to make a LM 386 mini amplifier. At first I made a push pull amplifier with a pair of 2SB 178 and 2SA 175 but it didn't work (2 times),so I decided to use an IC. As you can see in the picture the side part is messed up! I placed the tube outside the box as I was inspired by the jargon: a real radio glows in the dark! It's risky to have the parts on the outside because they could get broken. I placed everything on the outside the box to show everyone that this is an unusual radio!
The stereo plug-in in the top right is used as aerial and ground connection, the red for aerial and black for earth. The left knob is use as volume control and the other is for regeneration. My coil form was made from a paper towel cardboard tube. The coil looks dirty because I use cyanoacrylic glue to make wires stick tightly.
At first I built this set on a used disc box and battery powered. The reception is very good and clear. With just a 5 meter high antenna wire I can hear 22 AM stations in my local area and get 2-3 more overseas stations (mostly from Vietnam, Thailand, Kampuchea) when evening comes. But after I placed in the box and used the power supply, the sound is now distorted by hum noise. I guess it came from filter capacitor in the adapter part. I should increase capacity, mine used 1000 µf and a 350mA adapter transformer for 12 volts output. The hum noise is ruins the reception quality too, I lose stations, especially the overseas stations. I don't know why. But it doesn't bother me because cause I've hypnotized and mesmerized by the glow of the tube! So I named this project as: REAL RADIO GLOWS IN THE DARK!