You wake up one morning, open your laptop screen, only to see it black, but the computer is clearly powered on because you can hear the noise from the fans. Panic sets in quickly as you wonder what’s wrong. If you look very closely you can see a faint outline of what’s on your screen, and if you shine a flashlight on it, you can almost make out all of the images and text.
This is a very common problem with laptop screens, and typically only has 2 possibilities of the cause: the screens back light has gone bad, or the back light’s inverter has gone bad. The back light is basically a fluorescent bulb that sits behind your screen and lights it up enough to see everything clearly as you normally should. These bulbs can go bad occasionally, causing your computer’s screen to go black, and only show a faint outline of objects. The second possible cause, the back light’s inverter, has the same appearance when it goes bad as the back light itself does. The purpose of the inverter is to convert your laptop battery’s DC power back to AC power, which is required by your back light to work. If the inverter goes bad, the proper voltage will not be supplied to the back light, thus not illuminating it, causing a very dim screen. Sometimes, there are ways to determine whether it is your back light to blame, or the inverter to blame, just by the way your screen acts. Typically, when a back light goes bad, it will not illuminate at all, or it will illuminate the screen in a reddish hue, which may normalize as you continue to use your laptop, it is simple to diagnose if you’re experiencing the reddish hue by ruling out the video card. To rule out the video card, simply plug in an external screen to your laptop’s VGA port which will be on the back or side of your laptop. If after plugging into an external monitor you do not see any color distortions like you did before, you know that your back light has to be replaced, if you still see the same distortions on the external screen, then your video card is damaged. When an inverter goes bad, it is common for it to gradually get worse first, and your screen may stay lit for a short period of time before going dim, and then will re-illuminate after rebooting, only to go dim again within a short time. However, these are not rules that alone should be followed to provide an accurate diagnosis. Rather they are more of commonly experienced symptoms. To provide an accurate diagnosis, you must test your inverter and back light. There are special tools that are specifically for testing the inverter, but they can be rather expensive. Also, I would not suggest testing the inverter with a multimeter, as the voltage supplied by the inverter can be rather high.
First of all, in order to test your back light and inverter, you must have another laptop that has a fully functioning screen that you don’t mind opening. They do not have to be the same model or even brand, as the connectors are generally the same on all laptops.
Now, you must gain access to your laptop’s screen. To do so, remove the rubber screw covers around the screen with a flat head screwdriver, and place them glue side down on wax paper to preserve the glue. Next, remove all of the screws around the screen and place them aside in a safe spot. Do this and the next step to the laptop that works that you’ll be using to test the damaged one.
Next, run your finger underneath the bezel, all around the screen to remove the bezel.
Once you have removed the bezel, you should see a small board attached to the bottom of the screen with at least 2 cables coming out of it. This is the inverter. One cable comes from the laptop base and provides DC power to the inverter. The other cable(s) come out of the screen, and connect to the back light(s). If you see more than one cable coming from your screen connecting to your inverter, this means your laptop has multiple back lights.
Once both your damaged laptop and testing laptop’s screens are exposed, we will test the inverter on the damaged laptop. To do so, on both laptops, remove the cable(s) going from each screen to the inverter. Do not remove the cable going from the laptop base to the inverter. hp pavilion ryzen 5 Place both laptops very close to each other and plug the back light’s cable on the damaged laptop into the test laptop’s inverter. Turn both laptops on. If you can see everything as bright as normal on the damaged laptop, and it doesn’t go dim again after a short period of time, you must replace the inverter on your damaged laptop. At this point you’ve finished diagnosing the problem, and do not need to go on any further with this article. If the damaged laptop’s screen is still dim, and you can still see only a faint outline of the objects on the screen, then your back light(s) must be replaced.