820-2915 no power

[MDY]

Magsafe ok
PPBUS – 12.56V
3.42V present
SMC_RESET_L - 3.3V
SMC_ADAPTER_EN - 3.3V
PP3V3_S5 - 3.3V
32khz for PCH present
PM_PWRBTN_L - 3V
PM_RSMRST_L - 3V
PM_SLP_S5_L -0V
PM_SLP_S3_L -0V
PM_SLP_S4_L -0V
PP5V_S4 -0V

Any idea what to do next?

Board is pretty clean and no liquid damage.

 

[aprendiz]

R1800-R1803 voltage on both pins...

 

[MDY]

R1800-R1803 voltage on both pins: 3.3V ALL
PPVRTC_G3H (V RTC) - 3.3V
RTC_RESET_L (Reset RTC) - 3.3V

 

[dukefawks]

3V3_SUS and 5V_SUS present? Check for shorts on all rails.

 

[MDY]

Board power with 5V_S3 present one time and only cpu core was missing. But when I reconect the board it will not power anymore.
Now it is again as before. This mean no short there?
PCH bad?

 

[dukefawks]

Oh, intermittent power also. I bet this thing had an impact/dropped. Ripped traces under SMC/PCH possible. Avoid.....

 

[MDY]

When I short PM_PWRBTN_L to ground, I can see a pulse at PM_SLP_S5_L
This mean PCH respond, right? Could be bad PCH? Customer told me wasnot dropped.

 

[dukefawks]

Check for shorts on all rails. Fucked up reflowed GPU?

 

[MDY]

No shorts. No, GPU never reflowed. I doubt SMC or PCH.

 

[dukefawks]

Battery charging? Can it power on from battery?

 

[MDY]

Yes it charge the battery. Will not power on from battery. But I just put on the fan and realized that fan speed always for 1,2 seg.
I also noted that on coil 3V_S5 to ground is only 100ohm. Have a board to compare? Anyway I do have 3V_S5 present.

 

[dukefawks]

Pfff, now you tell me the fan spins.....

ALL_SYS_PWRGD coming high when fan is on? CPU Vcore?

 

[MDY]

fan spins - this is new for me. I dont know what happned. Now I also have pulse 0-5-0V at PP5V_S4
Nothing in R2584 ALL_SYS_PWRGD
PP1V05_S0 - appear for 0.5 seg

 

[dukefawks]

If there is nothing on ALL_SYS some rail is pulling down the power good. Check if all rails are coming on.

 

[MDY]

CPU core is not coming on. All other rails yes.

 

[dukefawks]

If all rails come up then ALL_SYS should be there.......

 

[MDY]

But I told you cpu core is low always. Is not that the reason that all_sys is low too?

 

[dukefawks]

Look at schematic and understand how ALL_SYS is generated.

 

[MDY]

Cannot find missing voltage.
Only suspect I have is L7720

It is PP1V5_S0
It goes only to 0.25V when I plug ac adapter.
To ground is 146ohm
Diode mode: 0.310 and 0.222

SOmebody have 2915 board to compare?

 

[dukefawks]

Since when is L7720 1V5? Pretty sure it is 1V8. 146 Ohm to GND should not be a problem, so dead U7720 is possible. I assume you checked enable is present.