Macbook air 820-00164-A not coming on

[Soji]

PP5V_S5 is present, PM_SLP_S4 is missing.
Signals that will make the PCH produce PM_SLP_S4_L are also present.
1.PPVRTC_G3H -3.3V
2. RTC_RESET_L 3.3V
3. PCH_SRTCRST_L 3.3V
4. PCH_INTVRMEN_L 2.3V
5. PCH_DSWVRMEN_L 2.3V
6. SYSCLK_CLK32K
7. PP3V3_S5 3.3V
8. PM_DSW_PWRGD 3.3V
9. PP3V3_SUS 3.3V
10. PM_BATLOW_L 3.3V
11. PM_RSMRST_L 3.0V.
Sometimes, PM_SLP_S4_L is intermittently present, but if I withdraw power and restore it, it goes missing again.
- With charger plugged in nothing happened
- Triggered SMC_ONOFF_L, there was no reaction at all.

 

[2informaticos]

"Signals that will make the PCH produce PM_SLP_S4_L are also present."
Don't make assumption so easy.
PCH will not release PM_SLP_S4_L until gets the drop pulse on PM_PWRBTN_L!
Check that when trigger SMC_ONOFF_L; supposing it has 3V steady.

 

[Soji]

PM_PWRBTN_L went low when I triggered SMC_ONOFF_L, it also has a steady 3.4V

 

[2informaticos]

Didn't note any pulse at PM_SLP_S4_L, at same time?

 

[Soji]

There was a pulse, but, it went to 1V and back to 0V

 

[2informaticos]

An o-scope can catch peak pulse; 3.3V probably.
If DC voltmeter shown 1V, there is pulse for sure.

That means S3 voltage pulse too; like L7520 and R8011.
Check PM_SLP_S3_L reaction too.

 

[Soji]

PM_SLP_S3_L was pulsing
PP5V_S4RS3 at L7520 was also pulsing
PP3V3_S3 at R8011 was also pulsing

 

[2informaticos]

Check for pulse at pins 7 & 3 of U1950.
Also check at CPU coils and PLT_RESET_L.

 

[Soji]

There's pulse at pin 3 and 7 of U1950
CPU coils L7320 and L7310 also has pulse
PLT_RESET_L was also pulsing

 

[2informaticos]

Any history available?
Possibly crap accumulated underneath PCH/CPU.
Try to burn it, using quality flux.