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Fan Spin - No Boot - No Display

2012 A1278 Model on the bench.

It turns on, fan spins, but that is it nothing else happens.The sleep light is on.

I have tried, removing RAM, Swapping RAM, Without the KB connected, Without a display, different HDD / SSD, Different working HDD cable, Reset SMC, PRAM etc..... Board looks clean, no water damage evident. Owner siad it just wouldn't start anymore. It does charge the battery though.

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What's good Livfe? This sounds like the CPU might not be executing?

It could also be a corrupted Bios.

For the CPU:

Check:

  • PPBUS_G3H (~12.6V)
  • PP3V42_G3H
  • PP3V3_S5
  • PP5V_S5
  • PP3V3_S0 (after power-on)
  • CPU core voltage (VCORE)

If VCORE never appears, the CPU isn't being enabled.

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Thanks, we will look into this and update with any findings :)

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