| MacBook Pro A1708 Not turning on, no current draw at 20V with no shorts repair | |
|---|---|
| Device | MacBook Pro A1708 |
| Affects part(s) | Motherboard |
| Needs equipment | multimeter, soldering iron, soldering station |
| Difficulty | ◉◉◉◌ Hard |
| Type | Soldering |
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Problem description
#incomplete
Symptoms
- Not turning on
- Drawing 0A (no current) on 20V as measured by USB-C meter
Solution
Diagnostic Steps
Check for low resistance to ground on SMBUS_SMC_5_G3H_SDA or SMBUS_SMC_5_G3H_SCL
On older MacBooks, this would result in no battery recognition and a lower voltage on PPBUS_G3H—on USB-C models, it actually results in the machine not turning on at all. Can be caused by a tiny speck of conductive material in the battery connector.
Check for 0.4 V in diode mode on SMBUS_SMC_5_G3H_SDA and SMBUS_SMC_5_G3H_SCL (red probe on GND)
if it's higher the I2C signals will look funny, not going just between 0 and 3.3 V. Check D6950—it can be blown when the SMC goes.
Check voltage on PPBUS_G3H
If you have no or low voltage on this rail, check the repair steps below.
Repair Steps
low resistance to ground on SMBUS_SMC_5_G3H_SDA or SMBUS_SMC_5_G3H_SCL
Clean the conductive material, Video
0.4 V in diode mode on SMBUS_SMC_5_G3H_SDA and SMBUS_SMC_5_G3H_SCL (red probe on GND)
#incomplete
Low or no voltage on PPBUS_G3H
It could be bad/dead ISL9239. Also check for ≈2.4 Ω on the two ISL9239 current-sensing circuits. If any of the 1 Ω or current-sensing resistors are blown, replace them first, or you will re-kill any new ISL9239 you try!