A1286 820-2915-A no boot

[hgoncalves]

Hi,

I have an A1286 820-2915-A that has green light, fan spin, big coils have voltage, CPU gets hot, but i get no usb activity.

Can you help?

 

[2informaticos]

Post CPU core voltage?
When board boots, it should drop from 1.15V to 0.75V.
Beeps RAM error when RAM is removed?

 

[hgoncalves]

Tks.

No RAM beep when removed.

PPVCORE_S0_CPU_PH1/2/3 sometimes starts at 1.15VAND drops to 7.5v, but them oscilates bettwen 7.5 and 0.5V.

Other times, they oscilates bettwen 1.15V and 0.144V

 

[2informaticos]

As far as I know, 7.5V is bigger than 1.15V.
And I'm pretty sure you've never got 7.5V at CPU core.
BTW, ALWAYS check DC voltage on the output pin of the coil, where the filter cap is connected.

Stable voltage at L7630?

 

[hgoncalves]

Hi,

Sorry, you're right. I had bad batteries on multimeter.

PPVCORE_S0_CPU_PH1/2/3 starts at 1.15V AND drops to 0.75V steady.

L7630 has stable voltages. 1.25V on pin1 and 1V on pin2

 

[2informaticos]

No need to check L7630, if already got correct VCORE.
Looks like your board boots and should get USB activity, or external image.
If not, there should be a GPU problem, which blocks the CPU after booted.

Easy to disable GPU on this board, to confirm the problem.

 

[hgoncalves]

Hi,
I have no USB activity nither external image.
I disabled external GPU with medusa, but still no usb activity.

 

[2informaticos]

Did you remove one of R8904/11 too?

 

[hgoncalves]

No i dindn't. Shall i remove them?

 

[hgoncalves]

OK, now i've removed R8911 and now i have usb activity. Is there other any way to solve this problem, without disabling / replacing the GPU?

 

[2informaticos]

Now you have to flash BIOS again, to disable GPU...