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How do I find out what is the missing signal or bad components that prevents the machin to power up ? I guess if U3900 could be the cause. What other signals should I check for in order to narrow down the search to the required ones for booting at least?

SMC_PCH_PWROK also 1,8V

I wonder if I get ALL_SYS_PWRGD_R I should also have PP1V8_S3, PP5V_S3, PP1V2_S3, PP1V05_S0, PP5V_S0, PP3V3_S0, PP1V5_S0, etc... Am I right?

Found 0,9v on L8102 No voltages on L7410, L7430, L7210, L7230 cpu get warm

Sure, I'll let you know when I'll get back to work tomorrow.

Something is preventing the board to go to s0. Ram voltage also ok

PM_SLP_S3_L allready measured... 3.3v stable

PM_SLP_S4_L solid 3.3 PM_RSMRST_L two seconds after enabling power goes to 3.3 stable no pulse

Once I press PWRBTN pch_pwrbtn_L goes low. That means PHC knows at least that have been triggered to power on. What next?

No other hints? Should I reallly let the customer bring this machine to Apple for a mobo swap?

by the way is it normal that in configurator 2 the macbook air is recognized as an Apple Controller? Just performed a new restore ended up with another padlock symbol ...???

yes solid 5v on L7670 and 3.3 V on L7690. Get also 12V on L7030 with no battery and when battery connected decreasing 4,5V during charge (charging normally I assume...) The customer said she previously nstalled Big Sur, may be the issue came after a furture update of the os? She also brig it to...

Sorry, didn't get a clear picture from the customer. "Suddenly It just stopped to boot...". I entered DFU, tried revive, no change, than tried a restore (they have a data backup...) finished with a big padlock symbol on the configurator 2 window which I definately ignore the meaning of (is it...

Sorry for the worts explanatory title ... forgot to edit before post it...

Got this machine that doesn't boot up but charges the battery. Non liquid spills at all, the board look very good. I get 20v on both usb C adapter voltmeter and most of the power rails seems to be solid except for the cpu s0 related power rails... CPU heatsink gets little bit warm but pressing...

Just realized the 85W adapter got the cable replaced with a 60W one... that should explain the issue...

Got this old machine with battery status indicator shorted and unable to boot. Fixed the battery charge indicator that solved the issue. Left off charge for 1 day performed a PRAM reset than stopped power on again with battery connected. Took out the logic board didn't start as well so I try the...

Great! Never tried manual resoldering of ram slots. Thanks

The only problem I'm experiencing so far it's with the ram slots that are both not reliable anymore. Sometimesthey works sometimes I have to re-insert the ram in the slot different times before it will be recognized. That was usually happening in the upper slot, don't know why I have it on both.

In the mean time I desoldered and read the SPI content... Found a completely blank SPI rom!!! Reprogrammed and now I finally got it booting! I wonder how could have the spi ROM been erased completely ?