LCD display window is not lighting up

If the LCD screen on your JL Audio JX250/1 amplifier is not lighting up when you turn it on, there may be a few possible causes:

• Faulty power connection: Check that the amplifier is receiving power by verifying that the power light is illuminated. If the power light is not on, there may be a problem with the power connection, fuse or wiring.
• Blown backlight: If the power light is on but the LCD screen is not illuminated, the backlight may be blown. In this case, the LCD screen may still display information, but it will not be visible without a backlight.
• Faulty LCD screen: If neither the power light nor the LCD screen are illuminated, there may be a problem with the LCD screen itself. This could be due to a faulty display panel, cable or connector.

An LED TV is still an LCD TV, just with LED backlighting. That model is an LCD TV. The difference is in the backlight. Both LED and LCD TVs use an LCD screen. LED TVs have LED backlighting of the LCD screen, which saves energy.

When the following conditions, namely the need to replace the LCD inverter:
No image on the screen, but the power light stays on
Dark display but still readable
Between the screen flashes on and off 1/2 to several seconds
Power light stays on, but no display and sound
No image on the screen, but LCD TV still has sound
Picture cycle on and off, as well as high-power LED lights
http://www.lcdinverter.info/dell-n26397-lcd-inverter-p-5754.html

When the following situations, you need to replace the LCD inverter:
No image on the screen, but the power light stays on
Dark display but still readable
Between the screen flashes on and off 1/2 to several seconds
Power light stays on, but no display and sound
No image on the screen, but LCD TV still has sound
Picture cycle on and off, as well as high-power LED lights
More:http://www.lcdinverter.info/acer-travelmate-8001-lcd-inverter-p-2046.html

When the following conditions, namely the need to replace the LCD inverter:
No image on the screen, but the power light stays on
Dark display but still readable
Between the screen flashes on and off 1/2 to several seconds
Power light stays on, but no display and sound
No image on the screen, but LCD TV still has sound
Picture cycle on and off, as well as high-power LED lights

When the following symptoms, that is, to replace a laptop LCD screen:
No image on the screen, but the power light stays on
Dark display but still readable
Between the screen flashes on and off 1/2 to several seconds
Power light stays on, but no display and sound
No image on the screen, but LCD TV still has sound
Picture cycle on and off, as well as high-power LED lights

The older LCD's have backlights hidden behind the display that burn out over a period of time, this is a tricky repair because the unit needs to be stripped down and the covering removed. Soldering skills for most jobs will be required.

Ok if you can see the image when you show a flashlight to it means that the backlight is not working, it could be a simple problem as the backlight power cable loose inside or in worst case the backlight completely damaged. Best to take it to a service center and they will be able to tell you what happened. Hopefully it's just a loose cable.As LCDs do not produce light themselves they need illumination (ambient light or a special light source) to produce a visible image. Backlights illuminate the LCD from the side or back of the display panel.Backlights are used in small displays to increase readability in low light conditions.You can search for info on Backlight to learn more about it.

Here's the manual:

http://www.alpine.com.au/downloads/web_owners_manuals/cassette_owners_manuals/TDA-7548E_TDA-7547E.pdf

you need to take the phone and have the LCD replaced