820-02098 power cycling

[Kyle93]

This arrived with no liquid damage. Power cycles every few seconds. Board looks pristine. Checked all coils and do not see any shorts.

When magsafe or usb-c is plugged in they both turn on for two seconds then off then on. All voltages appear as well.

What should be checked next?

 

[Kyle93]

Diode mode readings on all big coils look good as well.

 

[2informaticos]

Remove F5200/1 and check if C5250 voltage is stable.

 

[Kyle93]

Same issue is occurring with F5200 removed. C5250 voltage goes to 12.30v then drops to 0V while magsafe or usb-c is plugged in as they go off and come back on

 

[2informaticos]

Then you may have problems on the charger side; USB-C and Magsafe areas.

I recommend to check diode mode readings around U5200 and compare with good board.
You should check Q5230/40 too.

 

[Kyle93]

Checked diode mode in those areas and all of the readings are very close to a known good board.

What should be checked next?

 

[Kyle93]

Still waiting to hear back.

Diode mode readings match a good working board. Is there anything else that can cause this issue?

 

[x_Fil]

Still waiting to hear back.

Diode mode readings match a good working board. Is there anything else that can cause this issue

Is DFU mode stable or also exits from DFU after few seconds?

 

[2informaticos]

"You should check Q5230/40 too"
Tested out of board if open/close the channels?

 

[Kyle93]

Replaced Q5230/40 but no change

 

[Kyle93]

No luck entering dfu mode either

 

[x_Fil]

No luck entering dfu mode either

LID sensor disconnected?

 

[2informaticos]

Post U5200's basic voltages (keep F5200/1 removed): P_IN, AUX_DET, VDDA/P, EN_MVR, AUX_OK, A/BMON.
Any fluctuation?

 

[Kyle93]

P_IN flucuates up to 0.430v

AUX_DET 1.3V stable

VDDA/P 5V stable

EN_MVR - flucuates up to 0.465v

AUX_OK 0.056- 0.890v

A/BMON 0V

 

[Kyle93]

bad U8100? diode mode MPMU_BUCK0_LXO/3 0.100

0.223 on good board

 

[2informaticos]

U8100 is not involved yet, when F5200/1 are removed.
You should get stable C5250 voltage.
If not, you have problems on U5200, or power input areas.

U8100 may be bad, but remains to test later.

 

[Kyle93]

C5250 voltage is stable at 12.33v

What should be checked next?

 

[2informaticos]

First, resolder the fuse.

Check diode mode to ground on all secondary power rails.
Also check U8100 and U7700 LDOs.

 

[Kyle93]

PPVDD_ECPU_AWAKE is 0.633V

Removed L8200 diode mode on U8100 side is 0.525 while other side is 0.25

Is this bad M1?

 

[Kyle93]

PPVDD_ECPU_SRAM_AWAKE 0.702V