[wa2ise]

I took apart scrapping an old HP photo and document scanner/printer and salvaged the RGB light source
[Image: http://www.wa2ise.com/radios/LEDstick.jpg]
and used it in my homebrew cabinet AM/FM radio
[Image: http://www.wa2ise.com/radios/amfmdiallights.jpg]
Here I have it set up to have the dial light up cyan (blue and green, no red) when FM is selected, and light up a yellowish green (green and some red, no blue) when AM is selected. The green is always on, if AM is selected the red is turned on, if FM is selected blue is turned on. As the AM/FM switch power section switched the positive supply, I ended up using transistors to light up the desired LEDs in this common anode light stick.

The light stick uses red, green and blue LEDs, common anode. The LEDs light up bright enough with about 2ma DC current, and with all three LEDs with current like this, will burn about 30mW. Should be more than low enough for safe operation.

This stick is longer than the dail, but I didn't need to shorten it. Besides, there is a mirror of sorts at the far end, to reflect and distribute the light more evenly. I mounted this light stick to the inside of the cabinet about 5cm above the dial window, to get reasonably even lighting of the dial, and to avoid fouling the dial pointer mechanism. A long cable with a small connector connects the LED light stick to the radio circuitry.


[Image: http://www.wa2ise.com/radios/LEDinside.JPG]
The lightstick inside the radio cabinet. Note that I used some ty-raps as a strain relief near the head (the LED circuit board on this stick is thin and fragile) on the ribbon cable I used to connect the LEDs of the stick to the drive circuits (via a connector at the other end of the cable, away from the head). And the stick is at a slight angle, as the brightness was slightly higher near the LED head. Being a bit away from the dial helps make the dial lighting look a little more even top to bottom. Some of this LED light will reflect off the dial glass.

The above example radio is a solid state radio.  If the LEDs are burned out, or if you want to stick with technology that would have existed when your tube radio was made, remove the LED module from the lightstick head, and use an incandescent bulb instead. They could have made the lightstick out of glass, and they did have clear plastic in the day. You do need to be careful that the bulb's heat doesn't melt the lightstick plastic. . .