820-00138 - Fan Spins, Green Light, No Sign Of Booting / No Display

[mccafe]

Hello,

I have a MacBook that does not want to boot.
- We get a green light on the charger, fan spin, but no chime or display.
- External USB portable drive doesn't show any activity, seems brain dead.
- No signs of liquid damage.
- Tried clean ME region.

PPBCC_S0_CPU_PH1 / 2 / 3 = 1.7 volts

Any advice on how I should proceed with this? Thanks!

 

[2informaticos]

Any history available?
Tried new BIOS, or just cleaned ME on original?

Pins 2 & 4 of U2080 come high?
Check SMC_LRESET_L too.

 

[mccafe]

Customer turned it off one day and it never booted again.

I cleaned the ME region on the original. Pins 2 & 4 of U2080 = 3.3 volts. SMC_RESET_L = 3.3 volts. What I noticed is that high fan spin and as soon as I measure SMC_RESET_L, motherboard does a power cycle.

 

[2informaticos]

Try full known good BIOS.

 

[mccafe]

Thank you, it fixed it. After trying to write to the original BIOS chip another time, the chip failed completely. Unable to read or write to it. Got another one from a donor, flashed it with known good dump online and it now works.