Apple Macbook Air A1466 EMC2925 not booting, fan spinning, no chime.

[veedo]

Hi
I have a MacBook Air that was completely dead on arrival. During inspection I found a shorted capacitor near the SMC, which appeared to be the main fault. After replacing the capacitor, the short on the rail was cleared. The board then started recognizing the charger, charging normally, and the machine powered on. Initial testing outside the chassis showed normal behaviour.

However, after full reassembly a new issue appeared. There is no boot chime and no image on the screen, only the fan spins. The power button responds normally, it powers on without the charger connected and reacts to a forced shutdown. I also tested it without the SSD and the behaviour is exactly the same.

It seems like the machine is hanging very early in the boot sequence. What rails or signals would you recommend checking next. Could this be SMC related, SPI or BIOS corruption, or possibly a missing power good signal after reassembly. Any advice would be appreciated
A1466
820-00165-A

Thanks

[mon2]

https://logi.wiki/index.php/PM_SLP_S...roubleshooting

[mon2]

https://logi.wiki/index.php/G3_to_S3..._and_Broadwell

[reformatt]

Do you have CPU Vcore present? Assume so if you have fan spin. Are the power rails pulsing on/off or just stable? BIOS or missing power rails result in pulsing on/off every few secs.

If everything is stable, and there was corrosion around the SMC, first thing I do is reball the SMC.