A2337 5v 0.05a no boot sign.

[juyoung165]

The PPBUS_AON is showing 12.25V.. and I have found the following info. What should I check first?

• If the voltage is approximately 12.28-12.35V, it may indicate a communication issue between the SOC and PMICs, or corrupt firmware.

Edit: Not possible to get it into DFU mode.

PP3V8_AON_VDDMAIN present (3.9v) but no PP1V8_AON_MPMU... maybe bad U8100..?

 

[2informaticos]

First of all, welcome to the forum!

Any history available?

Check diode mode to ground at U8100 LDOs (page 34).
Don't bother with the ones marked "NC".

 

[juyoung165]

Firstly, all LDOs on U8100 are showing 0V.

I checked L8100, L82B0, and L8270 with my multimeter in diode mode, but the readings seem a bit off.

Sorry for asking such a basic question, but is it correct to measure in diode mode?

I've been using it without any issues so far, but this time the values seem a bit different from what I expected, so I'm a little confused.

 

[2informaticos]

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...

boards.rossmanngroup.com

You can compare the readings around U8100 and U7700 with good board, or referene table.

OpenBoardData Project

"all LDOs on U8100 are showing 0V"
I asked about diode mode, not voltage.

 

[juyoung165]

The picture is in diode mode, the value for L8100 0.026v. If this is correct way to reading values I will upload others too.

 

[2informaticos]

Red probe must be connected to ground.
Read the post I sent.

BTW, remember that I asked about LDOs readings, not coils...

 

[juyoung165]

I'm quite new to MacBook repairs, so I'm not entirely sure if I'm checking the right LDOs. Since I can find them using OpenBoardView, if there's anything else I should check, I’d really appreciate it if you could provide the names of the test points.

I tried Googling for a list of LDOs, but I couldn’t find much useful information. Apologies for my lack of knowledge.

PPVDD_PCPU_AWAKE = 0.021v
PPVDD_ECPU_AWAKE = 0.079v
PPVDD_CPU_SRAM_AWAKE = 0.192v
PPVDD_SOC_S1 = 0.026v
PPVDD_GPU_AWAKE = 0.030v
PPVDD_DISP_S1 = 0.148v
PP1V8_S2 = 0.285v
PP3V8_AON_VDDMAIN = 0.302v
PP3V3_S2_UPC = 0.414v
PP1V5_VLDOINT_MPMU = 0.200v
PP1V2_S2 = 0.291v
PP1V8_AON_MPMU = 0.301v

 

[2informaticos]

"Check diode mode to ground at U8100 LDOs (page 34).
Don't bother with the ones marked "NC""

 

[juyoung165]

Ah, I was being so dumb. Sorry about that!

PP1V2_S2 = 0.291v
PP3V3_S2_UPC = 0.415v
PP1V8_AON_MPMU = 0.301v
MPMU_VREF_ADC = 0.544v

 

[2informaticos]

Stop writing "V" for diode mode readings.
Avoid to create any confusion with voltage checkings.

Any of these lines get voltage?

 

[juyoung165]

Sorry for the confusion.

PP1V2_S2 = 0v
PP3V3_S2_UPC = 0.58v
PP1V8_AON_MPMU = 0v
MPMU_VREF_ADC = 0.61v

 

[2informaticos]

C8315 voltage?

Check PMU_SHDN and PMU_RESET_L voltages.

 

[juyoung165]

It seems like the BoardView file doesn’t perfectly match my board. I have the 820-02016-A board, but I can’t find PMU_SHDN.

C8315 (PP3V8_AON_VDDMAIN) = 3.78v
PMU_SHDN = cannot find
PMU_RESET_L = 0v

 

[2informaticos]

R8322 is not soldered, as expected.
But the corresponding pad is available.

Looks like bad U8100...

 

[juyoung165]

Ah.. I was most worried about this, but it turns out to be an IC issue.. I'll order 343S00438 and 343S00440 from AliExpress, replace them, and if it solves the problem, I'll leave a reply. Thank you!