820-00163 - Powers On - Fan Spin - Black Screen / No Post

[mccafe]

Hello,

I have a 820-00163 that powers on with a fan spin, but nothing else. Customer said it just suddenly stopped working. No corrosion found, board looks clean.

PPBUS_G3H = 12.6 volts
PPVCC_S0_CPU_PH1 = 1.8 volts
PPVCC_S0_CPU_PH2 = 1.8 volts
PPVCC_S0_CPU_PH3 = 1.8 volts
PPVCORE_S0_GFX_PH1 = 0.85 volts
PPVCORE_S0_GFX_PH2 = 0.85 volts

BIOS
1 SPI_MLBROM_CS_L = 3.3 volts
2 SPI_MLB_IO1_WP_L = 3.3 volts
3 SPI_MLB_IO2_WP_L = 3.3 volts
4 GND
5 SPI_MLB_IO0_MOSI = 0 volts ?
6 SPI_MLB_CLK = 0 volts ?
7 SPI_MLB_IO3_HOLD_L = 3.3 volts
8 PP3V3_SUS = 3.3 volts

When I plug in the power adaptor, pin 5 and 6 pulses two times to 0.5 - 1 volt and then goes to 0 volts

R6122 / SPI_MOSI / pin 1 = 0.474 diode mode
R6121 / SPI_CLK / pin 1 = 0.474 diode mode
R6111 / SPI_CLK_R / pin 1 = 0 volts / 0.48 diode mode~
R6112 / SPI_MOSI_R / pin 1 = 0 volts / 0.48 diode mode~

How should I proceed in troubleshooting this board?

Thank you in advance.

 

[mccafe]

Removed BIOS and pins 5 and 6 is now 3.3 volts each. Faulty BIOS chip it seems - checked with a programmer and I am unable to get a read from it? Where can I get a clean Rom to flash?

 

[2informaticos]

Instead of wasting time in such manner, did you think to check what happens on the BIOS chip of working board???
No matters what model is.
However, good to have 0V at mentioned pins.

Try this file, as is:

820-00163 clean ME fixed SSN.bin

drive.google.com

 

[mccafe]

I guess I got lucky. This one did the trick with a whole new BIOS chip + clean ME flash.

 

[mccafe]

I was about to reassemble the MacBook after further tests and the MacBook is back to not being able to post. Just a fan spin, responds to power off button, no backlight and that's it. This one is very odd.

 

[2informaticos]

Does the board work alone on the desk, but fails mounted on the shell?

 

[mccafe]

It currently fails both when mounted in shell and when board is alone on desk. No output to external monitor either. I tried new BIOS chip + flash several times already so it must be something else.

 

[2informaticos]

CPU gets core voltage?
PLT_RESET_L comes high?

 

[mccafe]

Yes, correct.

PPVCC_S0_CPU_PH1 = 1.8 volts
PPVCC_S0_CPU_PH2 = 1.8 volts
PPVCC_S0_CPU_PH3 = 1.8 volts
PPVCORE_S0_GFX_PH1 = 0.85 volts
PPVCORE_S0_GFX_PH2 = 0.85 volts
VR_PHASE_GPU_VDDCI = 0.9 volts

These are consistent and never changing.

PLT_RESET_L = 3.3 volts

Other random readings:
PP1V35_S3 = 1.35 volts
PP1V05_S0 = 1.05 volts

I checked all SPI bus series termination resistors, it checks out.

 

[2informaticos]

For random issues, broken trace/solders as possible culprit.