If the display has been gradually fading and is now unreadable, the fault is almost certainly loss of emission of the fluorescent display and it will need a replacement display module fitted (at a Bose Service Centre) Is there any sign of characters showing in a darkened room?
If it has suddenly gone off, with all other radio features are working as normal, but prior to this the display was bright and clear, and the set has not been subjected to a fall or a sudden sharp impact of some kind, (which can crack the display module and cause it to fail) then the most likely possibilities are; a failed filament supply to the display module, a failed high tension supply rail to the display module, or loss of data feed to the display. It is also possible there may be a fault in the day/night brightness switching circuitry that has shut the display down completely. It is not possible to be more specific without seeing the unit, or even knowing which model it is I'm afraid.
First, call BOSE to see if the unit is still under warranty. If so, send it to BOSE at your expense. If not, BOSE may offer to fix the unit for about $100 + shipping. If BOSE says they no longer service the unit, then you might be able to fix it yourself. The LED contacts may be corroded, loose, or disconnected. Unplug the unit, lift the CD lid, and you will see a screw. Use a Phillips head screwdriver to remove the screw. Turn the unit over, and remove the screws from the bottom. The upper shell should now be able to life off. Take care and do this slowly since the LED screen will be in the upper shell connected by a ribbon cable to the base shell. Check this cable to ensure it is making contact in the lower shell. The problem is likely to be contact with the LED screen in the upper shell. Carefully remove the ribbon and examine it to see if it is dull or green. Use an eraser to shine the ends of the ribbon cable. Blow away any debris and connect the cable to the LED again. Reassemble the shell, but do not screw it together. Plug the unit in. If the LED still does not light, the problem may be more complicated than can be addressed here. Good luck.
Answers & Comments
If the display has been gradually fading and is now unreadable, the fault is almost certainly loss of emission of the fluorescent display and it will need a replacement display module fitted (at a Bose Service Centre)
Is there any sign of characters showing in a darkened room?
If it has suddenly gone off, with all other radio features are working as normal, but prior to this the display was bright and clear, and the set has not been subjected to a fall or a sudden sharp impact of some kind, (which can crack the display module and cause it to fail) then the most likely possibilities are; a failed filament supply to the display module, a failed high tension supply rail to the display module, or loss of data feed to the display. It is also possible there may be a fault in the day/night brightness switching circuitry that has shut the display down completely. It is not possible to be more specific without seeing the unit, or even knowing which model it is I'm afraid.
First, call BOSE to see if the unit is still under warranty. If so, send it to BOSE at your expense. If not, BOSE may offer to fix the unit for about $100 + shipping. If BOSE says they no longer service the unit, then you might be able to fix it yourself. The LED contacts may be corroded, loose, or disconnected. Unplug the unit, lift the CD lid, and you will see a screw. Use a Phillips head screwdriver to remove the screw. Turn the unit over, and remove the screws from the bottom. The upper shell should now be able to life off. Take care and do this slowly since the LED screen will be in the upper shell connected by a ribbon cable to the base shell. Check this cable to ensure it is making contact in the lower shell. The problem is likely to be contact with the LED screen in the upper shell. Carefully remove the ribbon and examine it to see if it is dull or green. Use an eraser to shine the ends of the ribbon cable. Blow away any debris and connect the cable to the LED again. Reassemble the shell, but do not screw it together. Plug the unit in. If the LED still does not light, the problem may be more complicated than can be addressed here. Good luck.