We will be continuing maintenance on the wiki starting this Saturday at 9 am (UTC) to Sunday at 7PM (UTC).
There is a possibility of long maintenance-breaks and downtime during this time.
For more information contact us in the wiki Discord or by email at: firstname.lastname@example.org
MacBook Pro A2251 no Backlight on display repair
|This article is a stub. You can help Repair Wiki grow by .|
|MacBook Pro A2251 no Backlight on display repair|
|Device||MacBook Pro A2251|
|Affects part(s)||display board, main board|
|Needs equipment||multimeter, soldering iron, soldering station|
|Type||Micro-Soldering, Part replacement, Soldering|
Problem description[edit | edit source]
Identifying and solving backlight issues on the 820-01949 logic board, as well as similar boards from 2016-2020. A MacBook Pro with no backlight on the display is experiencing an issue where the screen remains dark even though the computer is powered on and operational. This means that while the computer itself may be functioning, the display is not emitting any light, making it extremely difficult or impossible to see the content on the screen. Shining a strong light on the display at an angle might reveal that the content is indeed present, but the backlight is not illuminating it.
Symptoms[edit | edit source]
- The display appears completely dark, with no visible content or backlight illumination.
- Occasionally, the backlight might flicker or flash briefly when the MacBook Pro is powered on or waking from sleep, but it remains dark after these brief instances.
- Connecting the MacBook Pro to an external monitor or TV results in a functional display on the external screen, confirming that the computer itself is working correctly.
Solution[edit | edit source]
Identifying the problem[edit | edit source]
This issue can be caused by multiple factors, you need to determine which one is present in your situation.
- Check for Backlight Output Short: Measure for a short to ground on backlight output (PPVOUT_LCDBKLT_F). Use C8471 (Figure 1) or adjacent capacitors for measurement; unplug the display connector to rule out issues with the TCON board or LED strip. Proceed to "Backlight output shorted to ground" repair steps if a short is present.
- Test with Known Working Display: If no short is found and there's no liquid damage history, test with a known working display. If backlight works, proceed to "Device has backlight output on a known good display, but not on the originally installed display" steps.
- Examine U8400 if corroded along with adjacent corroded components.
- If EDP_BKLT_EN is missing, U8400 is NOT the cause of the issue.
Solving the problem[edit | edit source]
Backlight Output Shorted to Ground[edit | edit source]
Identify and replace the shorted component. Check with and without the display connected. A short is commonly caused by a shorted capacitor. Inject 10v at 5 amps, thermally image the board, or use comparable short detection methods.
Device has Backlight Output on Known Good Display, But Not on Originally Installed Display[edit | edit source]
Replace the display assembly.
Corroded U8400[edit | edit source]
If U8400 is corroded or adjacent components are corroded, replace them.
Check pins 9 and 10; if corroded, connect them to R8400; Pin 9 to Pin 4, Pin 10 to Pin 3 (Figure 4).
Backlight Fuse (F8400) Blown in Absence of Short to Ground[edit | edit source]
Replace the backlight fuse with a compatible replacement (0603 package, 3 amp, 32v fuse).