Regarding the Nintendo Switch: the LCD screen lacks a backlight. The console boots up, emits sound, and responds to touch or button inputs, but the LCD appears to function only when illuminated by an external light source.
The console powers on and responds to inputs, but the screen itself does not seem to be working.
When you shine a light on the display, you can see the LCD functioning normally despite the lack of backlight; the Nintendo logo that appears upon startup is the easiest element to view when performing this test.
The issue likely lies with the LCD panel itself or the backlight circuitry.
First, you should test the unit using a known-good LCD screen. You can perform a “dry fit” test with a functional LCD without fully removing the original one—simply connect the bottom backlight cable or temporarily attach both the LCD ribbon cable and the backlight ribbon cable. Please refer to Figure 1 for the locations of these connectors.
If only the backlight ribbon is connected and the backlight circuit is functional, the screen will brighten slightly upon startup; if the backlight circuit is faulty, there will be no change in screen brightness.
If you wish to test with both the backlight and LCD ribbon cables connected, you will need to slightly bend the LCD cable rather than fully installing it. Exercise extreme caution when doing this; the LCD cable is fragile and prone to tearing, which could damage your known-good LCD screen.
If the backlight still fails to function when using a known-good LCD, the problem most likely lies within the backlight circuitry.
Begin by inspecting the backlight connector for damaged or loose pins.
The back of the Nintendo Switch motherboard showing the locations of interest for the backlight circuit; the backlight IC is circled in red, and test points are circled in blue.
Next, pull out the circuit board; test points are located on the side of the backlight connector opposite the connection interface, as shown in Figure 3. Set your multimeter to diode mode, connect the red probe to ground, and use the black probe to test each point marked in Figure 3. A reading deviation of more than 0.200V indicates a problem with the backlight IC or the capacitors surrounding it.
These three test points correspond to lines within the backlight circuit that are essential for proper backlight operation. Refer to Figure 4 to trace the path of each line. These points also connect to three of the four pins on the backlight connector (the fourth pin is a ground connection).
If a line shows a low reading or a short circuit during testing, you need to inspect the area around the components marked in Figure 4 for short circuits or corrosion.
If the line reads “OL” or shows a very high value, the issue is likely corrosion on the traces or pads beneath the backlight IC. If the leftmost test point shows “OL” (which is normal) or an abnormal reading, you might also have a faulty diode.
Corrosion caused by liquid damage is common; it can short-circuit or erode the pads under the backlight IC. Therefore, if you encounter abnormal readings but find no shorted components around the backlight IC—or if you have already removed or replaced any faulty components in the vicinity—you may need to reball or replace the IC itself.
Figure 5 shows an example of a backlight IC repair.
In this instance, the middle test point showed an “OL” (open circuit) reading. Liquid damage and corrosion had caused a break in the trace. To repair it, a jumper wire had to be run from the pad beneath the backlight IC to the pad below it; the backlight IC was then re-balled and soldered back onto the board. Once the broken trace was repaired, the Switch’s backlight functioned normally again.
