Macbook Air A2337, 820-02016-A stuck at 5V

[Jonnx]

Hello everybody,

I have seen a lot of posts about the A2237/A2338 about the 5V not boosting up to 20V issue, but none of them seem to have the exact problem as my board does.

My PPBUS_AON was measuring ~9.32V and the board kept power cycling, so I removed the fuse F5200 to measure PPVBAT_AON_CHGR_REG and indeed it was still 9.32V, but the board stopped power cycling. Then I measured U5200 values and got this:

U5200:
PPDCIN_AON_CHGR_R = 5.144V
AUX_DET = 1.287V
VDD = 2.767V
VDDP = 2.767V
AUX_OK = 0.848V
AMON = 0V
BMON = 0V

I think what stands out the most are the low VDD/VDDP values, which I know should be around 5V.
Is the next step to remove U5200? I would like to be absolutely certain there are no more possible culprits before attempting to remove it, as I am not that experienced yet with BGA repairs.

Thank you all for your time.

[mon2]

MacBook Air A2337 Not turning on, current draw cycling between 0.00 and 0.45a at 5V repair - Repair Wiki

[Jonnx]

Hello,

Thank you very much for your answer. I thought I had seen that post already, but to make sure I went ahead and measured and wrote down my findings:

1. L8100 / L8101 / L8102 (PPVDD_PCPU_AWAKE) (Figure 1) - Normal diode mode to ground reading ~0.033 / ~31.3Ω (Resistance)
2. L82B0 / L82B1 (PPVDD_ECPU_AWAKE) - Normal diode mode to ground reading ~0.120 / 119.1Ω (Resistance)
3. L8270 / L8271(PPVDD_CPU_SRAM_AWAKE) - Normal diode mode to ground reading ~ 0.241 / 240.6Ω (Resistance)
4. L8120 (PPVDD_SOC_S1) - Normal diode mode to ground reading ~ 0.04 / 39.5Ω (Resistance)
5. L8110 / L8111 / L8112 (PPVDD_GPU_AWAKE) - Normal diode mode to ground reading ~ 0.044 / 43.5Ω (Resistance)
6. L8280 / L8281 (PPVDD_DISP_S1) - Normal diode mode to ground reading ~ 0.208/ 207Ω (Resistance)
7. L8290 (PPVDD_DCS_S1) - Normal diode mode to ground reading ~ 0.277 / 276.5Ω (Resistance)
8. L84E0 - (PP1v4_LDO_PREREG) - Normal diode mode to ground reading ~ 0.301 / >170kΩ and climbing (Resistance)

Although the values sometimes don't seem to really match the ones in the post, I am nevertheless not getting a short anywhere.

But i noticed something weird. With the battery and the charger connected, I thought the SYS_DETECT_L was supposed to get pulled low, but instead I get random voltage jumps in the <1V region and therefore PP3V8_AON_VDDMAIN and all inherited voltages aren't present.

Does this mean that something could be wrong with the battery? I am a bit stumped.

Have a nice week
Jonnx