Kenwood TR-7950 LED Back Lights

My old Kenwood TR-7950 though still a good radio had seen better days with the back lighting for the LCD display. The little bitty bulbs are not only difficult to find but they get hot, melt plastic, and burn out. I had replaced them several times so this time I figured that this was gong to be the last time. The pictures below give you an idea of what I did.
 
Here's how it looks after the mod is complete.
 

The lamp behind the channel knob was the easiest.
 
You can see the two holes where the bulbs were recessed. See how the left one is discolored from the heat of the bulb. There was melted plastic in that hole.
 
The head doesn't have to be removed but it does have to be loosened and folded downward. You will have to disconnect the connector to the volume/squelch/power control and to the display board.
 
There is another bulb on the right, between the two connectors, mounted on the opposite side of the circuit board right next to the edge. It provides illumination for the DTMF pad. In this case I replaced it with a white LED. I changed the series resistor to a pair of 680 ohm 1/4 watt resistors in parallel.
 
The whole radio opened up.
 
This photo was taken with no flash and a small amount of ambient light.
 

As you can see here, the display is evenly lit and looks nice.
 

The blue LEDs makes the entire radio look new.
 
You can see the white LED lighting the DTMF key pad in this picture.
 
The source of the LEDs was The Electronic Goldmine http://www.goldmine-elec.com/
(thanks to Gene - N0MQ for reminding me to put this link on here)
Click "order on line" then " view catagories" then "LEDs". Select "T 1 3/4" and you will find a huge assortment of LEDs to choose from. The ultrabright LEDs are the ones I used and provide the best light for current comsumption. You will want to pick series ballast resistors for your LEDs to limit the current through them to 20 ma which is the optimum for light output and LED life.
 

 

Page updated November 20, 2006