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This 2015 Air board generates all power rails, Vcore, ALL_SYS_PWRGD, and PM_SLP_S4_L. Fan spins but does not POST, chime, or start up. The only abnormal signals I noticed are SMC_PROCHOT = 3.4 and CPU_PROCHOT_L = 0. Any ideas?
Check all SPI Bus Series Termination resistors and their traces.
Inspect board for corrosion.
Check it outside of shell, only charger and USB device for test.
Do not connect LIO flex, nor SSD and airport card.
Close inspection revealed a tiny speck of corrosion on one corner of the SMC. Anything I can do to the SMC that doesn't involve replacing or reballing it?