Macbook Pro 14 2021 - A2442 - 820-02098-A not turning on 5v fluctuation

[Rickkap]

I would like some help with this MacBook if possible. It came in with not turning on and the Magsafe light was off. After inspecting the logicboard i cannot find any liquid damage and also no burnt or shorted components.
took some measurement and i can see i have fluctuation on PP3V3_S2 and also PP5V_S2_MAIN amongst other rails. Using the thermal camera RC282 & RC283 were pulsing, but after removing these it was still the same.

I then did some investigation into why the rails were pulsing and noticed that P5VS2_PWR_EN (comes from U8100) is also doing the same thing.. Replaced both U8100 and also U7700 from a working (iCloud locked) logicboard, still the same. I've also temporarily removed all the components on the PP3V3_S2 rail but the fluctuation is still there so i'm thinking that it could be coming from a higher rail. I'n not sure what the power rail startup sequence is on this model. All the AON rails are fine and stable and now i've hit a wall and not sure what to do next.

[Rickkap]

Anybody willing to help!!!

[mon2]

Check the frequency of MPMU_XTAL2 and MPMU_XTAL_R.

[spidertnt]

https://www.badcaps.net/forum/troubl...no-power-a2779

sometimes failed caps repeat ...worth a check

[Rickkap]

Check the frequency of MPMU_XTAL2 and MPMU_XTAL_R.

32Khz and stable on both sides of R8350

[mon2]

What is the voltage and current draw of the USB Type C meter?

[Rickkap]

It's 5.18v current draw fluctuates between 0.00 and 0.05A and that's on all 4 ports

[mon2]

Each PD controller is a suspect. Confirm the LDO rail of each controller - much like the CD3215 article:

https://logi.wiki/index.php/CD3215_Bootup_Sequence

The BMC 1v1 will only be active for the USB C port being used to power the board.

[Rickkap]

My understanding is that these boards don't have the T2 and are not similar to the CD3215. I took it upon myself to swop from an icloud locked board, all 4 CD3217 in the correct order along with the ROM's as explained on this page https://logi.wiki/index.php/CD3217_a...er_on_Sequence and it is still fluctuating.

I've spent enough time on this now so it's become another donor or until someone else gets and fixes the same issue.

[mon2]

https://boards.rossmanngroup.com/thr...acement.64959/

[nhosic]

Rickkap, have you found any solution to this one? I have the same exact issue here. Spotless board. Pulsing RC282 and and RC283. My thinking was the same as yours. Start replacing ICs around the 5V_S2 and 3V3_S2 lines, but I don't want to waste time if this isn't the issue.

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of PP5V_S2_MAIN @ LC260 (either side). What is the resistance in ohms?

[nhosic]

I can't find any lines not shorted to ground at all - the board looks spotless. Diode mode is .342 on each side. Resistance to ground is 5 megs.

[mon2]

What is the voltage to ground of P5VS2TPS_PWR_EN (measure @ RC260)? This is the ENABLE signal for this power rail that is absent.

[nhosic]

0.7 volts

[nhosic]

I'm wondering if U8100 just kind of fried because it is responsible for a lot of these smaller power rails, just don't want to harvest and reball such large BGA chips for no reason.

[mon2]

Carefully measure the voltage to ground of:

SMBUS_BATT_SCL
SMBUS_BATT_SDA

[Rickkap]

I never found the solution for this problem, i did think it could be the SOC which was faulty and in the end i gave up. I must have replaced so many components but it wouldn't stop fluctuating. If i was you i wouldn't bother try to fix it, plenty of man hours wasted