Let me guess. You have a Monsoon radio right?
The problem is probably not the bulb but a
HAIRLINE crack on a solder joint. You can fix it. It's not as hard as it sounds. You'll have to take the face plate off the front to get to the circuit board. Use a magnifying glass to find the crack solder joint. A bad solder joint usually looks gray and dull instead of shiny silver. Or You can put a dab of solder on all the joints. The crack is very small but you can see it if you look close.
Here's some more links>>
http://www.ls1tech.com/forums/stereo...t-working.html
http://www.ls1tech.com/forums/stereo...backlight.html