820-3209

[arnonabuurs]

Hello, I have an 820-3209 that was working and suddenly stopped (its our mac). Got green and orange light. After inspection saw some corrosion near U7600, replaced C7601, R7641, R7642 and R2801. Now i got all voltages upto 0.9v, including 1.05v on L7630. Whats missing is power on L7550 PPVCORE_S0_CPU. I got 8.4v on Q7550 pin 1. What else should be present for this to work?

On U7400 pin 1 I got 0.008v, that should be 3.3v to enable? CPUIMVP_TON is 8.39 measuring OK
At Q9750 I measure as follows:
Pin 1 = 0.7v (should be 1.05v?
Pin 3 = 0.086 Pin 4 same
Pin 7 = 0.75v
Pin 6 = 3.25v
Pin 5 = 0.48v

 

[2informaticos]

"On U7400 pin 1 I got 0.008v, that should be 3.3v to enable?"
It comes from ALL_SYS_PWRGD, so yes 3.3V is normal.

If R7974 is OK, check why AL_SYS_PWRGD is missing.
Corrosion at U1950?

BTW, I cannot find Q9750 in schematic...

 

[arnonabuurs]

Sorry its Q7950.
And I cannot find U1950 in schematic, i read they are numbered different for 3209? My board is 820-3209-A

 

[arnonabuurs]

OK got it, its U2750 and that signal comes from U7960, will check. R7974 is OK

U2750
Pin 1: 0.086v
Pin 2: 0.025v
Pin 4: 0v
Pin 5: 3.3v
R2750 = ok

At Q7950 I measure as follows:
Pin 1 = 0.7v
Pin 3 = 0.086 Pin 4 same
Pin 7 = 0.75v
Pin 6 = 3.25v
Pin 5 = 0.48v
All resistors around it measure OK and no liquid around both these IC

 

[2informaticos]

Yeah, U1950 usually on newer boards.
U2750 output OK, as missing ALL_SYS_PWRGD.

"Pin 5 = 0.48v"
Too low.
You can remove U7950, not really needed; just a redundant protection...
However, be sure 3V3_S0 is OK.