A1398 2012-early2013 15” MacBook Pro Retina

Resolder U8900 until GPU Vcore is 0.9 V regularly. This is an incredibly common issue people will report, and 99% of the time, it is bad soldering on U8900.

Use the Hakko 2032 micropencil with a T30-KN tip to fix.

U7000 ISL6259 bad, shorted current sense resistors R7021 and R7022 to ground through the U7100.

https://www.youtube.com/watch?v=O0sDWN0Pnio

• PP5VS5 was 1.1 V instead of 5 V.
• Broken U7501 due to corrosion.
• https://www.youtube.com/watch?v=W3zs3p8SEsM

• PM_SLP_S4_L missing for random reason. This can be caused by corrosion at RTC circuit, example: https://www.youtube.com/watch?v=efsk7rR12Zs
• Bad right I/O board. Unplug it, see if it works(short on 3.3 V or 5 V rail on the I/O board can cause this problem).
• Not using genuine 85W charger. Smaller wattage chargers won't boot board, PM_BATLOW_L will be near 0v.

• ADAPTER_SENSE not 3 V due to bad DC in board.
• PP3V42_G3H missing.
• SMC not working (if SMC is off, you will have 12.23 V on PPBUS_G3H instead of 12.56 V) because it is dead, not turning on(SMC_RESET_L low).

In at least some of the cases (SMC, maybe the other problems as well?) the machine will draw ≈100 mA (Louis thought that important enough to put that in the title on the 2020 January 13 video, that one was a dead SMC)

• Keyboard bad, shorting PP3V42_G3H to ground or power button stuck on.
• Bad U6901/U6900.
• https://www.youtube.com/watch?v=O0sDWN0Pnio

• There was a lot of corrosion on board, U7400 (TPS51916) and ISL6259 were replaced as were a number of other corroded passives.
• A number of traces were repaired with jumper wires.
• The SMC was not turning on as PPBUS_G3H was still at 12.24 V instead of 12.56 V
• Further troubleshooting revealed a broken trace (inside the board) between the diode and the SMC. A jumper wire was ran and this finally fixed the MacBook.
• Video source: https://www.youtube.com/watch?v=PFcPZLOuMoo

First, try a known good battery.

If it doesn't work, check PPBUS_G3H. If it is 12.23 V, the SMC is not communicating with the battery on its data line, either because the SMC is bad, or because the pull-up resistors on the data line are bad. On rare occasion U7000 can pull down the data lines. There is a shared data line between the battery, SMC, and ISL6259(U7000). If PPBUS_G3H is 12.56 V, then you probably have a bad battery.

Watch - https://www.youtube.com/watch?v=g85FqqkZiaE

Make sure the issue is caused by no backlight, and not no image! This board often has no image due to U8900 issues!

• Blown backlight fuse (the 820-3332 does not have a current sensing circuit for backlight, so the fuse can still blow on this model, unlike older models.)
• Short to ground on backlight output(if backlight fuse blown, check this).
• Bad screen/screen cable — if backlight voltage is 49–50 V, bad screen.
• Short caused by a capacitor on underside (next to C103 marking) value of cap is not known

You can fix the screen if the cap/connector on the screen is bad, it just sucks to do. But it is the only option this screen is no longer available.

Resolder U8900 until GPU vcore is 0.9 V regularly. This is an incredibly common issue people will report, and 99% of the time, it is bad soldering on U8900.

Use the Hakko 2032 micropencil with a T30-KN tip to fix.

If it works on an external but not on internal, check that L9000 wasn't blown by someone shorting the 5 V line to the screen to ground.

After fixing U8900 when you find that 5 V is still missing on L9000 and LCD_PWR_EN is missing on U9000, do not chase, 99% of the time this turns out as a no fix, usually bad iGPU or MUX communication issues.

Resolder LCD connector

Solution: Replace the U7100, if it is broken, along with the faulty resistors.

Symptoms: MacBook not turning on. Causes: Using a knockoff charger.