820-2936 Green Light

[computercaverva]

At first the board had no green light, I injected 16v just after the DC In fuse and had a MagSafe connected and got the green light but no fan or other signs of life. I then replaced the U7000, Q7080, Q7085, Q7030, Q7035, U74000. After removing the ISL I also made sure that all of the Current Sense resistors were good. Now I connect the MagSafe only no DC Power supply and get the Green light but no fan. There are no 5v or 3v rails and PPBUS_G3H is 0.170v @ F7040.

 

[dukefawks]

I have to ask why you are just replacing parts, what does U7400 even have to do with this? This has now introduced a whole bunch of uncertainties.

First thing to check would be resistance to GND on PPBUS, then resistance between pins 17/18 27/28 of U7000. Then check R7005.

 

[computercaverva]

Sorry I should've mentioned that the board had signs of previous repair around the FETs and U4700 so I went through and replaced them as the solder job looked questionable.

Resistance to GND on PPBUS: Starts at 0L then starts decreasing in the 16 M Ohm range

Pin 17/18 U7000: 2.9 Ohms

Pin 27/28 U7000:19.9 Ohms

R7005:20.1 Ohms

 

[dukefawks]

Remove F7040 to rule out PPBUS being pulled down by the system. If there still is no 12V on L7030 there is an issue around U7000, bad soldering/dead U7000.