A2337 820-02016 power won’t turn on

[Araibu]

Thank you for your guidance. I understand now that the readings in diode mode are not actual voltages, but are generated by the multimeter which injects a constant current on the board. I will make sure to avoid using "V" after diode mode readings to prevent any confusion with voltage checking in the future.

Looks to have very low values around U8100.
Just for test, remove L8120/1 and R810C; check where the low value remains.

I understand that I should check again in diode mode after removing L8120, L8121, and R810C. Is my understanding correct?

 

[2informaticos]

Diode mode, or even ohm scale for such low readings.

 

[Araibu]

Thank you for your guidance.I will report back with the results.

 

[Araibu]

I was able to remove the L8120 component, but I’m having a hard time removing the L8121 component from the motherboard. Could you please give me some tips on how to do this?

I removed and checked the L8120 and R810C components. Here are the results:
L8100→0.017
L8110→0.022
L8120-1→0.449
L8120-2→0.020
L8230→0.305
L8270→0.179
L8280→0.106
L8290→0.226
L82B0→0.059
L84E0→0.277
I noticed that the values of L8120-1 and L8120-2 were different, but everything else was the same.

 

[2informaticos]

"values of L8120-1 and L8120-2 were different"
Once the coil is removed, cannot get the same value on both pads.

But you need to remove L8121 too, for proper test.
Apply 138 degrees solder paste on its pads.

Also keep R810c out of board; until test is done.

 

[Araibu]

Thank you for your advice. Thanks to your suggestion, I was able to remove L8121.
Upon rechecking, I found the same results as before.

L8100→0.017
L8110→0.021
L8120-1→0.449
L8120-2→0.019
L8230→0.305
L8270→0.179
L8280→0.106
L8290→0.226
L82B0→0.059
L84E0→0.278

 

[2informaticos]

Looks like bad M1 CPU...

 

[Araibu]

Thank you for your reply. I apologize for the inconvenience.
If the PP3V8_AON_VDDMAIN line is shorted, is there a way to find the cause without using a constant current source?

 

[2informaticos]

You didn't mention any short there before.
What's the exact ohm value of the short?

Voltage injection method can be used when the resistance to ground is low enough to sink a current which will heat something on the board.
If temperature is not high enough, a performant thermal camera is required.

 

[Araibu]

Sorry for the oversight. After checking, the ohm value is 0.4Ω
I also have a HIKMICRO thermal imaging camera.

 

[2informaticos]

Start injecting with just 1V; don't go above 4V anyway.
Set PSU amp limit to max first.

 

[Araibu]

Sorry, I do not have a PSU. Could you please suggest another method?

 

[2informaticos]

Sorry...
Get lab PSU; recomended adjustable 30V/20A.
You've got IR camera before a PSU???

 

[Araibu]

I have obtained a PSU and I also have an IR camera.
Could you please tell me which component I should start injecting from?

 

[2informaticos]

You must inject voltage into 3V8_AON power rail; as there is the short to ground.

 

[Araibu]

I used a PSU to inject 1V from C5894. Since L8300 was hotter than the surrounding components, I replaced it, but the issue wasn’t resolved. Could you please advise?
I have a cooling spray.
Should I also check the covered areas like UF100 and UF000?

 

[2informaticos]

If L8300 got hot, then U8100 is the first suspect.
Lift L8300 and check which side the short remains.

 

[Araibu]

I lifted L8300 and checked, and both sides are shorted.

 

[2informaticos]

I mean to check resistance to ground on the coil pads on the baord; once the coil is out.

 

[Araibu]

I measured the resistance and got the following results:

MPMU_BSTLQ_LX: 0.3Ω
PP3V8_AON_VDDMAIN: 28.5Ω

The resistance for PP3V8_AON_VDDMAIN is gradually decreasing.