820-00239 No Boot, liquid damaged

grmacs

Member
Not much liquid residue on the board. Seems like came in most near display control connector of course.

Some noticeable stuff in near u7100 at r7100, c7100. on other side of board around one side of u7220. Customer noted display started discoloring in one corner before it was shut down.

PPBUS G3H is 13V
ALL_SYS_PWRGD - 0V
PP5V_S4 shows voltage going to zero. Diode here to ground is .295V


From what I've seen here in forums this board CPU often gets overvoltage w/liquid damage. I don't want to waste a lot of time on this as it if it is low probability fix.

SOme quick things to check?
 

grmacs

Member
J8500 looks clean on board and in cable connector. No sign of liquid or shorting on pins. Another shop tried drying it out for customer. They must've been in the mac because one of the cable pull tabs was missing. So I don't know if they cleaned the board connectors at all. I don't think so or I would think they would have seen residue in spots on the board.

Pin 1 diode= 0.264V
Pin 3 diode= 0.268V

Here is a summary of areas where there was liquid residue:
C/R7100/1
U7220
C7210 to C8006
 
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grmacs

Member
Yeah... that and the fact that the damn display controller is right in the direct path of potential liquid, I'm wondering if the display is any good either. SO keyboard is 99% chance of being toast. SOunds like CPU is 75% or more of being dead, any way to get a guess on display?
 

grmacs

Member
I gave it one last poke around and noticed good voltage on
ALL_SYS_PWRGD & PP5V_S4
PUt it back in mac with one USB-C, display, one speaker and keyboard connected and get fan spin high. No display and no chime, no external display. If CPU fried still common to see basics work, correct?
 

2informaticos

Administrator
Staff member
"ALL_SYS_PWRGD - 0V
PP5V_S4 shows voltage going to zero.
----------------------------
noticed good voltage on
ALL_SYS_PWRGD & PP5V_S4 "
What happened?
Do you get VCORE now?
 
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grmacs

Member
Not sure what happened... I had cleaned those areas... but thought had taken readings since cleaning.

pp5v_so_vcore1= 5.16V
 

grmacs

Member
When 1st powered on VCORE is 1.1V about 5secs after fans kick in (~10 seconds after power), it drops to 0.62V, at about 15secs from power on it pops to 1.1V but then immediately back to 0.62V and fans pick up speed to full on. It then holds at 0.62V
 
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