MACBOOK A1466 WIFI ISSUE REAPEAT

[Instafixx]

Device came in for no wifi. U3540 was heating up. Replaced - Issue resolved.
It came back again after 2 weeks. Replaced U3540 again and it was fine.
It has come back again. I seem to miss something.

Nothing heats up now.
Voltages at U3540
Pin 7/8 are 0V.
Pin 2 is 0.6V. It should be higher I think. No shorts.
3v3_WLAN is okay.
Bad R3554/5 ?
Resistance across pins
R3555 is 30k Ohms
R3554 is 111k Ohms

Checking board on bench.

 

[2informaticos]

Pin 2 should be 3.3*100/(100+232)V; aprox 1V.

High value resistors must be measured out of board.

 

[Instafixx]

I replaced R3555 and R3554. Still its 0.6V

 

[2informaticos]

Increase R3555 value; test with 150-180K.

Not sure what is U3540's VREF level, but 0.6V can be close to it.
In such case, a slight drop on SENSE pin, can reset the Wifi module.

 

[Instafixx]

Issue Resolved. Thank you.