Macbook Air 820-3437-B USB Power

[Shredplayer]

Hi, i have a Macbook Air 2014 820-3437-B logic board with non working USB port, i have 5v on PP5V_S4RS3 on pins 2 and 3 but 0v on PP5V_S3_RTUSB_A_ILIM pins 6 and 7, pin 8 is 3v
so i replaced u4600 but i still have no 5v on pins 6 and 7, i then checked USB_PWRT_EN on pin 4 and i got 0.80v, i then checked PM_SLP_S4_L on R8117 and i got 2.3v, 100 ohms on R8117, my best guess is i have problem on my USB power enable but no idea whats next.

 

[2informaticos]

Please confirm which USB port doesn't work; just onboard J4600, or both.
You can remove U4600 and check if USB_PWR_EN comes on high.

Any history available, liquid damage?

 

[Shredplayer]

Macbook Air works fine without any liquid damage, both ports not working, removed the u4600 USB_PWR_EN is 0.80v

 

[2informaticos]

Change R8117 and check continuity with U4600 enable pin.

 

[Shredplayer]

R8117 measures correct in and out of circuit but replaced it anyway with new one and now USB ports works, thanks

 

[Shredplayer]

Back with the same problem, after few hours of usage USB ports don't work anymore, R8117 USB_PWR_EN is 0.80v , PM_SLP_S4_L on R8117 and i got 2.3v

 

[Shredplayer]

i removed u4600 again and measured USB_PWR_EN still 0.80v, whats supposed to be the voltage of USB_PWR_EN?

 

[Shredplayer]

USB_PWR_EN to ground is 58 ohm? is that a short?

 

[JohnB8812]

Yes that?s too low

 

[2informaticos]

If you get 58 ohms after U400 removed, you have a inside board leakage.
In this case, solder R8117 on pin 1 only and run tiny wire from its pin 2 directly to pin 4 of U4600.
But you MUST cut off the trace from pin 4 to the rest of board.

I suppose R/C8114 are not soldered and no corrosion present on their pads.

 

[Shredplayer]

Just to make sure before i do that, u4600 removed then R8117 pin 1 = 2.3v and pin 2 = 0.80v, i then removed R8117 and i then checked PM_SLP_S4_L on R8117 pin 1 pad is measured 3.3v, does it confirm there's a leakage on R8117 pin 2 pad to u4600 pin 4?


with R8117 abd u4600 removed here are the resistance to GND

R8117 pin 2 pad = 121 Ohms
R8117 pin 1 pad = 94 Ohms

 

[Shredplayer]

If you get 58 ohms after U400 removed, you have a inside board leakage.
In this case, solder R8117 on pin 1 only and run tiny wire from its pin 2 directly to pin 4 of U4600.
But you MUST cut off the trace from pin 4 to the rest of board.

I suppose R/C8114 are not soldered and no corrosion present on their pads.

Cut the trace before the pin 4? will that disable also USB_PWR_EN on J9500 pin 3?

 

[2informaticos]

Oops, I forgot too search for all occurrencies of that signal.
In this case, check diode mode to ground disconnecting LIO flex.
Your problem could be in LIO board.
If still low, inspect J9500 for corrosion.