Charger stuck at 5V instead of 20V on MacBooks and MacBook Air A2337 No backlight on display repair: Difference between pages

MacBook Air A2337 No backlight on display repair
Device	MacBook Pro A2337
Affects part(s)	display board, main board
Needs equipment	multimeter, soldering iron, soldering station
Difficulty	◉◉◉◌ Hard
Type	Soldering, Part replacement

Latest revision as of 15:21, 29 October 2023

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Problem description

No backlight on display on the 820-02016 Logic Board, The laptop turns on, LCD is displaying a picture but without backlight.

Symptoms

Example image (Figure 1) -- No image yet. Help expand this page by uploading it!

Detail all measurable or observable symptoms in this section.

No Backlight
All voltage rails are normal
Possible liquid damage/corrosion

Solution

Diagnostic Steps

Failed display TCON board or a failed display LED strip

Check for a short to ground on backlight output (PPVOUT_LCDBKLT)
- CP860 or adjacent capacitors in the series is an appropriate area to measure, since it does not require removal of the system board.
- If a short to ground is measured, unplug the display connector to rule out a potential short to ground within the TCON board or LED strip of the display.

Short to ground on backlight output caused by a failed output decoupling capacitor (Most common)

Check for a short on the backlight output while the screen is unplugged
- CP860 or adjacent capacitors in the series is an appropriate area to measure, since it does not require removal of the system board.
If the short is persistent with the screen unplugged, proceed to the "Backlight output shorted to ground" repair steps below.

Failed backlight driver (UP800)

UP800 is in a prime spot to be hit with liquid on the 820-02016 and is very commonly seen to be corroded after history of liquid damage.
- Failure of UP800 without the presence of liquid damage is uncommon, however if you have no backlight with a known good display, and do not have a short on backlight output, UP800 may be bad or you may have another circuit fault such as a bad resistor or broken trace within the UP800/backlight generation circuit.
- If UP800 is corroded, replace it along with any other corroded resistors or capacitors adjacent to it.
It is common for current sensing pins (pins 9 and 10) of UP800 to be very corroded with corresponding pad/trace damage.
- gently scrape the coating off of the traces going to pins 9 and 10 of UP800 and run jumper wires from the traces to pins 9 and 10 of UP800.
- 0.02mm jumper wire is recommended.
Ensure that the backlight circuit has its input voltage (VIN) by measuring on BOTH SIDES of FP800, which is the backlight fuse.
- Voltage on both sides of the fuse should be equivalent to PPBUS_AON.
- If the backlight fuse is blown, check for a short on backlight output (PPVOUT_LCDBKLT) and on backlight input (PPVIN_LCDBKLT_F).
- If the fuse is blown without a short, proceed to the "Backlight fuse (FP800) blown in the absence of a short to ground" repair steps below.
Check that the backlight circuit is being enabled, the screen will need to be connected for the enable signal to be sent out.
- measure voltage on RP842. BKLT_EN_R / BL_PWR_EN should measure around 1.8v while a GOOD known display is connected.
  - If backlight EN is missing, be sure that you do not have a parts issue with your display or logic board to display cable.
  - BKLT_EN missing on this board due to a board issue is very rare, but may be cause by a failed PMIC (U8100) or failed iGPU in the M1 SoC itself.
Ensure you have continuity between pin 1 of RP831 (LCDBKLT_FB_XWR) and PPVOUT_LCDBKLT.
- Although rare on this board, it is worth checking to see if the backlight feedback trace is blown. Without feedback, the backlight driver will not produce its output.
Check the 5v input to UP800 (PP5v_BKLT_A and PP5v_BKLT_D).
- RP845 or RP844 may blow if UP800 fails. Ensure you have 5v on both of the above listed lines. If low, replace the blown resistor(s) and UP800.
If you have VIN (PPVIN_LCDBKLT_F), Enable (BKLT_EN), and both 5v lines (PP5v_BKLT_A and PP5v_BKLT_D), and no backlight output with the absence of a short to ground, replace the backlight driver (UP800).

Repair Steps

Backlight output shorted to ground

Find and replace shorted component How to find short circuits
- Ensure the short is not caused by the display. Be sure to measure with and without the display connected.
- Most commonly, a short on backlight output is caused by a shorted capacitor.

Device has backlight output on a known good display, but not on the originally installed display

Replace the display assembly. Use only a display for a A2337 MacBook Pro. Earlier Intel MacBook displays will not work.

Backlight fuse (FP800) blown in the absence of a short to ground

Replace the backlight fuse with a fuse from a donor board or a compatible replacement.
- 0603 package size, 3 amp, 32v fuse. Brand does not matter.
Before applying power be sure to double check for a short to ground. Check for a short to ground on backlight output and backlight input.

PP5v_BKLT_A or PP5v_BKLT_D absent or low

Ensure PP5v_S2 is present to both resistors prior to replacing any components
- If PP5v_BKLT_A is absent or low, replace RP845 and UP800.
- If PP5v_BKLT_D is absent or low, replace RP844 and UP800.

@@ Line 1: / Line 1: @@
-{{Explanatory Guide
+{{Repair Guide
-|Type=Circuit
+|Device=MacBook Pro A2337
-|Difficulty=2. Medium
+|Affects parts=display board, main board
+|Needs equipment=multimeter, soldering iron, soldering station
+|Type=Soldering, Part replacement
+|Difficulty=3. Hard
 }}
-USB-C MacBooks get charged through their USB-C ports, using USB-C PD standard which allows to deliver high power through a USB-C connector by raising the voltage higher than the regular 5 volts we've been used to on legacy USB ports. This requires a handshake between the laptop and the charger through a dedicated data bus, so that the charger can tell the laptop what its capabilities are, and so the laptop can then request a higher voltage, if available.
+{{stub}}
-*PP3V3_G3H missing due to a short circuit on the input to PP3V3_G3H creation circuit
+==Problem description==
-*Corroded LDO capacitor for PP3V3_G3H around a CD3215. On boards with 4 ports, on right side of board, check under shielding by SSD under the right CD3215 for hidden corroded capacitor.
+No backlight on display on the 820-02016 Logic Board, The laptop turns on, LCD is displaying a picture but without backlight.
-*PP3V3_G3H missing due to PM_EN_P3V3_G3H missing due to bad ISL9239
-*PP3V3_G3H missing due to CHGR_EN_MVR missing due to bad ISL9240. ISL9240 is not available for purchase. Donor would be required. Watch this troubleshooting video on similar 15" model (A1990) https://www.youtube.com/watch?v=HJ2jyo7pAmE
-*PPVIN_G3H_P3V3G3H missing due to a short to ground, check D6902 if PP3V3_G3H voltage drops lower than 3.4V after fixing PPVIN_G3H_P3V3G3H short
-*Bad CD3215
-*Bad CD3215 ROM chip (U2890)
-*Corroded probe points on the data lines between ROM chip and CD3215
-*Corroded resistors around ROM chip (U2890 or UB090) affecting communication between ROM chip and CD3215
-*Corrupted T2 firmware (when applicable)
-If the issue is a bad CD3215, one way to get an idea, is to see which does not boot loop. When you plug the charger in with the USB-C current meter, it will turn on for 2-3 seconds, then turn off and turn on again. Whichever port doesn't boot loop usually has an associated CD3215 that is bad. Also, the bad CD3215 will occasionally get hotter than the rest.
-CD3215s are chips made by Texas Instruments specifically for Apple, and are likely custom versions of their TPS65986 chip. Texas Instruments do not sell them, so replacement chips must be taken off donor boards.
+==Symptoms==
+[[File:Placeholder image.jpg|thumb|Example image (Figure 1) -- No image yet. Help expand this page by uploading it!]]
+Detail all measurable or observable symptoms in this section.
-There are multiple revisions of them, CD3215B, CD3215C, ... They are not compatible with each other, so make sure that you always replace a CD3215 with one from the same revision.
+*No Backlight
+*All voltage rails are normal
+*Possible liquid damage/corrosion
-Troubleshooting CD3215s:
+==Solution==
-*Check presence of PP3V3_G3H, required to power the chip
+===Diagnostic Steps===
-*Check presence of all 4 LDOs (3.3V, 1.8V, 2, 1.1V)
-*If an LDO is missing, check for short
-*If no short, and only the 1.1V LDO is missing, it can be because the CD3215 can't load its firmware. Typically this also makes that USB port to not bootloop. Two options:
-**It is the master CD3215, directly connected to the SPI ROM. In that case, check continuity of SPI bus signals, possibly look at them with a scope while applying power to the board
-**It is the slave CD3215, not directly connected to the SPI ROM. In that case, it will request firmware to the other CD3215 through UART port (UPC_XX_UART_TX and UPC_XX_UART_RX). In that case, it is possible that the other CD3215 is bad
-*If other LDOs are missing but no short, replace the CD3215
-*Once all CD3215s have all LDOs up, then it's a matter of talking to the SMC. Check I2C bus signals for activity.
-*Can also be a dead / bad ISL9239
+====Failed display TCON board or a failed display LED strip====
-T2 firmware can also cause the machine to be stuck at 5V. It is however, important to rule out other possible causes for the issue before re-flashing T2 firmware. Typically machines that have corrupted T2 firmware will be stuck at 5V 0.0A and typically will have PPBUS present and PP3v3_S5 missing. PP5V_S5 will often be present. T2 firmware can be re-flashed via Apple Configurator 2, however this will erase data in most cases. Try a "soft" re-flash first by clicking Advanced Options > Revive Device in Apple Configurator 2.
+*Check for a short to ground on backlight output (PPVOUT_LCDBKLT)
+**CP860 or adjacent capacitors in the series is an appropriate area to measure, since it does not require removal of the system board.
+**If a short to ground is measured, unplug the display connector to rule out a potential short to ground within the TCON board or LED strip of the display.
+====Short to ground on backlight output caused by a failed output decoupling capacitor (Most common)====
+*Check for a short on the backlight output while the screen is unplugged
+**CP860 or adjacent capacitors in the series is an appropriate area to measure, since it does not require removal of the system board.
+*If the short is persistent with the screen unplugged, proceed to the "Backlight output shorted to ground" repair steps below.
+====Failed backlight driver (UP800)====
+*UP800 is in a prime spot to be hit with liquid on the ''820-02016'' and is very commonly seen to be corroded after history of liquid damage.
+**Failure of UP800 without the presence of liquid damage is uncommon, however if you have no backlight with a known good display, and do not have a short on backlight output, UP800 may be bad or you may have another circuit fault such as a bad resistor or broken trace within the UP800/backlight generation circuit.
+**If UP800 is corroded, replace it along with any other corroded resistors or capacitors adjacent to it.
+*It is common for current sensing pins (pins 9 and 10) of UP800 to be very corroded with corresponding pad/trace damage.
+**gently scrape the coating off of the traces going to pins 9 and 10 of UP800 and run jumper wires from the traces to pins 9 and 10 of UP800.
+**0.02mm jumper wire is recommended.
+*Ensure that the backlight circuit has its input voltage (VIN) by measuring on BOTH SIDES of FP800, which is the backlight fuse.
+**Voltage on both sides of the fuse should be equivalent to PPBUS_AON.
+**If the backlight fuse is blown, check for a short on backlight output (PPVOUT_LCDBKLT) and on backlight input (PPVIN_LCDBKLT_F).
+**If the fuse is blown without a short, proceed to the "Backlight fuse (FP800) blown in the absence of a short to ground" repair steps below.
+*Check that the backlight circuit is being enabled, the screen will need to be connected for the enable signal to be sent out.
+**measure voltage on RP842. BKLT_EN_R / BL_PWR_EN should measure around 1.8v while a GOOD known display is connected.
+***If backlight EN is missing, be sure that you do not have a parts issue with your display or logic board to display cable.
+***BKLT_EN missing on this board due to a board issue is very rare, but may be cause by a failed PMIC (U8100) or failed iGPU in the M1 SoC itself.
+*Ensure you have continuity between pin 1 of RP831 (LCDBKLT_FB_XWR) and PPVOUT_LCDBKLT.
+**Although rare on this board, it is worth checking to see if the backlight feedback trace is blown. Without feedback, the backlight driver will not produce its output.
+*Check the 5v input to UP800 (PP5v_BKLT_A and PP5v_BKLT_D).
+**RP845 or RP844 may blow if UP800 fails. Ensure you have 5v on both of the above listed lines. If low, replace the blown resistor(s) and UP800.
+*'''If you have VIN (PPVIN_LCDBKLT_F), Enable (BKLT_EN), and both 5v lines (PP5v_BKLT_A and PP5v_BKLT_D), and no backlight output with the absence of a short to ground, replace the backlight driver (UP800).'''
+===Repair Steps===
+====Backlight output shorted to ground====
+*Find and replace shorted component [[How to find short circuits]]
+**Ensure the short is not caused by the display. Be sure to measure with and without the display connected.
+**Most commonly, a short on backlight output is caused by a shorted capacitor.
+====Device has backlight output on a known good display, but not on the originally installed display====
+*Replace the display assembly. Use only a display for a A2337 MacBook Pro. '''Earlier Intel MacBook displays will not work.'''
+====Backlight fuse (FP800) blown in the absence of a short to ground====
+*Replace the backlight fuse with a fuse from a donor board or a compatible replacement.
+**0603 package size, 3 amp, 32v fuse. Brand does not matter.
+*Before applying power be sure to double check for a short to ground. Check for a short to ground on backlight output and backlight input.
+====PP5v_BKLT_A or PP5v_BKLT_D absent or low====
+*Ensure PP5v_S2 is present to both resistors prior to replacing any components
+**If PP5v_BKLT_A is absent or low, replace RP845 and UP800.
+**If PP5v_BKLT_D is absent or low, replace RP844 and UP800.