Technical Support Apple 820-3115-B

lazaro089

Registered
Golden

Reputation:

I have an 820-3115-B (A1278). Fanspin, no video.
I'm on S0 state. I have PLT_RST_L =3.3V But no CPUIMVP_AXG_PGOOD.
Doing some readings, i checked for CPUIMVP_UGATE1G on the oscilloscope. The U7400 isn't trying to switch the MOSFET. Checked for CPUIMVP_VR_ON (U7400 enable signal) I'ts 3.3V.

CPUIMVP_PGOOD = 3.3V also.

So CPU it's getting power but Integrated Graphics isn't. Already tried another two U7400 from a donor board. Also changed Q7550

CPUIMVP_UGATE1G = 0V.
 

Hosein Asadolahi

Staff member
Registered

Reputation:

I have an 820-3115-B (A1278). Fanspin, no video.
I'm on S0 state. I have PLT_RST_L =3.3V But no CPUIMVP_AXG_PGOOD.
Doing some readings, i checked for CPUIMVP_UGATE1G on the oscilloscope. The U7400 isn't trying to switch the MOSFET. Checked for CPUIMVP_VR_ON (U7400 enable signal) I'ts 3.3V.

CPUIMVP_PGOOD = 3.3V also.

So CPU it's getting power but Integrated Graphics isn't. Already tried another two U7400 from a donor board. Also changed Q7550

CPUIMVP_UGATE1G = 0V.
check PM_MEM_PWRGD and PM_MEM_PWRGD_R signal
 

lazaro089

Registered
Golden

Reputation:

Sorry for the late response. It goes UP to 3.3V Then 320ms after, it goes down.
 

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lazaro089

Registered
Golden

Reputation:

Sorry, I gave you a wrong reading.
In my previous post I posted the reading for PM_MEM_PWRGD_L

PM_MEM_PWRGD is stable at 1.5V
 

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