I have a Fluke ScopeMeter 97 that's come in really handy over the years. Before I got it, it was a sales rep's demo unit, so it was used pretty hard. The screen backlight is an electroluminescent panel, and their intensity can fall off pretty dramatically over their life. This particular display is also transflective, which makes it extremely readable under direct sunlight, but means the backlight is essential to using it in indoor lighting. To use it in the past, I'd shine a bright desk light on it, but I've always wished the backlight would just work.
I finally took the meter apart and checked that the driver circuitry was putting out a reasonable voltage and frequency — it was. Clearly, the EL panel was just shot. Searching around, I found several sources for replacement panels, but I ended up going with one at SparkFun since I needed a few other things from there anyways. The cool thing about EL panels is that you can cut them to whatever size and shape you want, as long as you leave the electrodes attached. The original panel was 3.5" so this 10cm panel would be perfect. I tried to copy the active area of the old panel and trimmed the panel to size, ensuring to trim off the side that would leave the most of the edge electrodes connected, and sealed the edges with clear tape.
Of course, the original panel was connected by spring tabs near one edge, while the connector on my replacement panel was soldered and in the center. I was able to make this work by tucking the wires along the edge of the LCD and soldering them to the large pads originally for the spring tabs. I also had to cut out a few notches in the plastic to get enough clearance for the tab.
I put it all back together and … IT WORKED!!
Edit: Here are a few more photos and details about the LCD assembly. As before, only do this if you are comfortable working on things, and at your own risk.
There are two screws that hold the top cover on, and there are two more screws in the battery compartment that hold the back case on. With those removed, you can swing the back cover open. The LCD is attached to the board with 3 spring clips, which are visible from the back side with the board still installed. There are a few screws through the board that will need to be removed, then the board can be lifted out of the case. Once the board is free of the case, the three spring clips can be carefully pried off. Then, the LCD assembly will come free of the board. There are alignment pegs at each corner, so the main concern is keeping the contact pads on the board and the contact strip on the LCD assembly (gray with a black stripe through it) clean and in position. If you put things back together and end up with lines in your display, disassemble everything, make sure there are no specks of dust or oils on those, and reassemble. It may take a few tries if the alignment gets messed up, but it's possible to get it back right. On my LCD, the backlight was just held on by 4 pieces of tape. Very carefully, peel off the tape, and remove the old EL panel. Remember, you are working with the LCD itself. At this point, how you proceed depends on the panel you were able to find. In my case, I had to cut it to size, making sure to leave as much of both electrodes as possible; then I had to run wires from the tabs on the new panel over to the tabs on the board. Once that was done, assembly was just the reverse of the above.