MacBook Air A1466 does not turn on from keyb ON/OFF button

[mferna14]

Dear buddies., working on a MacBook Air A1466 (Logic Board 820-00165-A 2017). The logic board turns on fine (This is all done without battery) & the Magsafe jack is lit to orange. I boot it up to OS. Once I shut it down, it does not turn on again unless I remove the magsafe 2 jack & put it back again. There is no liquid spill & the voltages seem to be fine. I re-build a new BIOS & CleanME region done, but the problem still exsist. Once shut down, does not turn on from the keyb power ON/OFF button. I put in a new keyboard & the MagSafe/Audio board & a new flex cable too, no luck, still the same. Any tips will be appreciated, thanks in advance.

[mon2]

Try using the shorting ON/OFF button pads with tweezers on the logic board to mimic the pushbutton action. Do they work?

[mferna14]

Thanks mon2 for this tip.. Do you mean "Disconnect touchpad and short SMC_ONOFF_L to ground instead of pressing power button on the keyboard"... I will do this in the morning when in the workshop. & I just read my previous posts., same kind of problem I was facing on another 820-00165-A & then I had to replace the SMC. Hopefully this time it not.

[mferna14]

mon2., I shorted SMC_ONOFF_L to ground, does not turn on. Then I removed the old SMC, & under it the solder was dry, it came off easily. Put in another known good SMC but the problem is still there, Does not turn on with the pads on the logic board. But with the pads shorted with the tweezer, it turns off fine but does not turn on. Any more tips pls. Thanks dear.

[mon2]

Confirm the default (parked) voltage to ground of SMC_ONOFF_L. That is, this line cannot be floating and must have a pull-up resistor. Only then can the short to ground event cause a trigger due to the high to logic low transition.

[mferna14]

mon2., I had to fix this so today I gave the laptop some more time. I checked J4800 connector & there was some wierd/abnormal voltages with only the magsafe cable connected (NO BATTERY) on PP3V3_S4_IPD (Pin 10) & TPAD_SPI_INT_S4_WAKE_L_CONN (Pin 13) which was always high (nearly 2.8V). Whereas when only the magsafe cable is attached & NOT turned on, this should be 0 volts. Tracking back this was a PP3V3_S4 switch & was always on. This volts generated from U8000 & on Pin A1 & B1 (OUTPUT) of this chip should give 3.3V i.e when turned on. In my case this volts (2.8V) was always present. Before replacing the chip I checked the Ohms, & was only 34Ohms, here sould be around 300K. Replaced U8000 (TPS22924) & all worked like charms. Turns ON & OFF from anywhere, from the pads or the Keyboard ON/OFF button. Thanks mon2 for all the tips & guiding me, all the best & meet you in the next diagnosis.