Sadly I dont have that much troubleshooting experience yet. Have rebuilt some backlight circuits and repaired the common iPhone errors so that's something.
The board Im working on now 820 4924 stopped working because of liquid damage and didn't turn on but with a light on the charger. Got the board out and it took around 36mA. Got the first few G3H lines as normal so went ahead to clean up the dirty corroded areas:
U3740
Q5480
Q1840
Q1842
I first was confused by the PPBUS_G3H being 12.5V for a macbook since I worked more on MBA's. Expected it to be 8.6V so looked around the ISL6259 and replaced it with a donor. PPBUS stayed the same and found out that the voltage is normal for the MBP's. Now it's starting around 44mA and working to 49-51mA after a few seconds. This after replacing the ISL and cleaning up. These are a few rails to get an idea:
PPBUS_G3H = 12.5
PPBUS_S5_HS_COMPUTING = 12.5
PP3V42_G3H = 3.42
PPBUS_S5_HS_OTHER5V = 12.5
PPBUS_S5_HS_OTHER3V3 = 12.5
PPVRTC_G3H = 3.32
PP3V3_SUS = 3.32
PP5V_S5 = 5.0
PP3V3_S5 = 3.32
PP3V3_SUS = 3.32
PP5V_S4 = 0
PPBUS_S4_X239 = 0
PPVIN_S0_CPUVR = 12.53
Looking around the web I expected that an S4_EN signal is maybe missing since I couldn't find any shorts on the S4 rails which might cause all S4 rails to be pulled to ground. Trailing back some S4_EN signals gets me to big BGA chips. When it is not reaching an S4 state, what would be some of the first useful enable signals to check? Or is there something that Im overlooking right now?
Thanks in advance!
The board Im working on now 820 4924 stopped working because of liquid damage and didn't turn on but with a light on the charger. Got the board out and it took around 36mA. Got the first few G3H lines as normal so went ahead to clean up the dirty corroded areas:
U3740
Q5480
Q1840
Q1842
I first was confused by the PPBUS_G3H being 12.5V for a macbook since I worked more on MBA's. Expected it to be 8.6V so looked around the ISL6259 and replaced it with a donor. PPBUS stayed the same and found out that the voltage is normal for the MBP's. Now it's starting around 44mA and working to 49-51mA after a few seconds. This after replacing the ISL and cleaning up. These are a few rails to get an idea:
PPBUS_G3H = 12.5
PPBUS_S5_HS_COMPUTING = 12.5
PP3V42_G3H = 3.42
PPBUS_S5_HS_OTHER5V = 12.5
PPBUS_S5_HS_OTHER3V3 = 12.5
PPVRTC_G3H = 3.32
PP3V3_SUS = 3.32
PP5V_S5 = 5.0
PP3V3_S5 = 3.32
PP3V3_SUS = 3.32
PP5V_S4 = 0
PPBUS_S4_X239 = 0
PPVIN_S0_CPUVR = 12.53
Looking around the web I expected that an S4_EN signal is maybe missing since I couldn't find any shorts on the S4 rails which might cause all S4 rails to be pulled to ground. Trailing back some S4_EN signals gets me to big BGA chips. When it is not reaching an S4 state, what would be some of the first useful enable signals to check? Or is there something that Im overlooking right now?
Thanks in advance!