A1708 20V, 310mA, no boot

[MicroSMD Lab]

I'm working on a A1708 Macbook Pro 820-00840 that came in with a missing ISL9239 from another shop. The owner said it fell and stopped working and the other shop said the ISL9239 was cracked. I replaced the ISL9239 and I'm getting 20V, 310mA, the fan spins for about 15 seconds then the current drops to about 30mA and goes back up to 370mA but no more fan spin and no boot.
I get 12.97V on PPBUS_G3H and PP3V3_G3H is present 3.404V. Voltages on the inductors are L7670=5.07V, L7690=3.3V, L7730=1.05V, L7370=1.04V, L8060=1.0V, L7900=1.0V, L7960=0.951, L8030=1.2V which seems normal.
But L7210=0.2mV with a 2.8ohm resistance to gnd.
Any advice will be much appreciated.

[MicroSMD Lab]

Re: A1708 20V, 310mA, no boot

PPBUS_G3H_CPU=12.97V, PP5V_S0=5V, VCINP_P5VU7310=5V
Maybe U7210 is defective?

[piernov]

Re: A1708 20V, 310mA, no boot

Check voltage on PM_EN_CPUVCC_R, CPU_VIDALERT_L, CPU_VCCST_PWRGD

[MicroSMD Lab]

Re: A1708 20V, 310mA, no boot

Thanks again for the help piernov!
PM_EN_CPUVCC_R = 3.219V
CPU_VIDALERT_L = 111.4mV
CPU_VCCST_PWRGD = 0.990V

[piernov]

Re: A1708 20V, 310mA, no boot

No idea, it could be that the CPU isn't requesting VCore. I don't have enough experience with this board to know if CPU VCore comes up even if the CPU doesn't request it.
Make sure there's no damage around U7100.

[MicroSMD Lab]

Re: A1708 20V, 310mA, no boot

Visually nothing looks damaged around U7100. Will start probing tomorrow. There's a video by REWA where they test all the inductors I listed earlier to determine if the board is functioning properly, L7210 (PPVCCCPU_S0G_PH1) is one of them which they have 0.648V as normal.
This is the link to the video
https://www.youtube.com/watch?v=3DP6qBUiSdU&t=849s

[MicroSMD Lab]

Re: A1708 20V, 310mA, no boot

I've noticed that the current increases from 310mA to 320mA and when this happens the CPU heats up then it drops back to 310mA and the CPU cools down a little. It seems to be cycling this way.

[piernov]

Re: A1708 20V, 310mA, no boot

But while it's cycling, PPVCCCPU_S0G voltage stays flat at 0V?

[MicroSMD Lab]

Re: A1708 20V, 310mA, no boot

Yep, no change in PPVCCCPU_S0G. Is it possible to use a 820-01041 board to investigate if the CPU request Vcore? Please pardon me if I'm asking an irrelevant question.

[piernov]

Re: A1708 20V, 310mA, no boot

Power sequence is pretty different since 820-01041 is a T2 machine and the CPU VCore regulator is configured differently.

[ErikNL]

Re: A1708 20V, 310mA, no boot

I'm working on a A1708 Macbook Pro 820-00840 that came in with a missing ISL9239 from another shop. The owner said it fell and stopped working and the other shop said the ISL9239 was cracked. I replaced the ISL9239 and I'm getting 20V, 310mA, the fan spins for about 15 seconds then the current drops to about 30mA and goes back up to 370mA but no more fan spin and no boot.
I get 12.97V on PPBUS_G3H and PP3V3_G3H is present 3.404V. Voltages on the inductors are L7670=5.07V, L7690=3.3V, L7730=1.05V, L7370=1.04V, L8060=1.0V, L7900=1.0V, L7960=0.951, L8030=1.2V which seems normal.
But L7210=0.2mV with a 2.8ohm resistance to gnd.
Any advice will be much appreciated.

Did you find the problem?

got the same problem here with a A1708. 20V - 0,35A on Usb-c meter and fan spin for 10-15sec but after that no response while votage and amps stay the same. Also Mouse light is turning on when plugged in.

PPVCCGT_S0G = 0.000 Diode mode, 3.6 ohms, 0V
PPVCCCPU_S0G = 0.000 Diode mode, 7,8 ohms, 0,96V

for good hopes i also replaced U7100 and did a pram reset after but no difference

anyone else also experience this problem to?

[mon2]

Re: A1708 20V, 310mA, no boot

hi.

1) Review the attached diode coil readings. Some of the values are fuzzy but hope you can still read them.

2) What is the reading @ F7000 for the voltage when ON ? Power down, and remove the battery. Then place your meter in RESISTANCE mode -> what is the resistance reading to ground on F7000? It is good to review the same for other coils on the board.

Perhaps you have a shorted (bad) cap onboard and the resistance will be very low. The Vcore rail is ok to be low but list the values. If the value is too low, the power supply will current limit the power supply so that it does not get killed.

[d.rectcer]

Re: A1708 20V, 310mA, no boot

Did you find the problem?

got the same problem here with a A1708. 20V - 0,35A on Usb-c meter and fan spin for 10-15sec but after that no response while votage and amps stay the same. Also Mouse light is turning on when plugged in.

PPVCCGT_S0G = 0.000 Diode mode, 3.6 ohms, 0V
PPVCCCPU_S0G = 0.000 Diode mode, 7,8 ohms, 0,96V

for good hopes i also replaced U7100 and did a pram reset after but no difference

anyone else also experience this problem to?

Did you find the solution? I have exactly the same problem as yours. I already put clean me EFI dump but it doesn't help.