Hello Guys,
I have a 820-00875 board here which is not booting. Fan spin for some seconds but no boot, actually I saw it booting once but then after putting passcode screen became black and system freezed.
History
Mac was working normally and then system freezed with a screen glitch. The customer then rebooted it and it started but stop after he put passcode (same behaviour wich I saw once. No prior repair on motherboard just a changed battery some months ago.
Diagnosis
Checked all power lines all present as well as ALL_SYS_PWRGD that sits at 3.3V. L7370, L7220, L8060 and L7900 got 1V stable (I think they should drop around 0.6V) while L7210, L7420, L7410 and L7430 got 0V. L7730 is 1.05V
Usb ampmeter start 5v then 12.6 and sits at 20.2V once there it goes from 0.02a to 0.20 then sits at 0.32a (battery disconnected, board on desk). Occasionally loop back to 0.02a and come high to 0.32a
CPUVR_PWM1 and CPUVR_PWM2 bot at 5V
CPUVR_FCCM is 0v which might be the culprit. This signal should be generated by U7100
Looking under thermal camera u7330 got 35 degrees celtius on the left up corner (around pin 2,1,12). CPUVR_FCCM is not shorted to ground.
Resistance for big coils as follow:
L7370 7.7 ohm
L7220 4.8 ohm
L8060 42.6 ohm
L7900 32 ohm
L7210 5.5 ohm
L7420 2.4 ohm
L7410 2.4 ohm
L7430 2.4 ohm
L7730 397 ohm
At first stage based also on graphic glitch before shut down described by the customer I thought was cpu fried but after I saw it booting once I have some hope for this board so I need some guidance.
Thanks in advance for any help.
I have a 820-00875 board here which is not booting. Fan spin for some seconds but no boot, actually I saw it booting once but then after putting passcode screen became black and system freezed.
History
Mac was working normally and then system freezed with a screen glitch. The customer then rebooted it and it started but stop after he put passcode (same behaviour wich I saw once. No prior repair on motherboard just a changed battery some months ago.
Diagnosis
Checked all power lines all present as well as ALL_SYS_PWRGD that sits at 3.3V. L7370, L7220, L8060 and L7900 got 1V stable (I think they should drop around 0.6V) while L7210, L7420, L7410 and L7430 got 0V. L7730 is 1.05V
Usb ampmeter start 5v then 12.6 and sits at 20.2V once there it goes from 0.02a to 0.20 then sits at 0.32a (battery disconnected, board on desk). Occasionally loop back to 0.02a and come high to 0.32a
CPUVR_PWM1 and CPUVR_PWM2 bot at 5V
CPUVR_FCCM is 0v which might be the culprit. This signal should be generated by U7100
Looking under thermal camera u7330 got 35 degrees celtius on the left up corner (around pin 2,1,12). CPUVR_FCCM is not shorted to ground.
Resistance for big coils as follow:
L7370 7.7 ohm
L7220 4.8 ohm
L8060 42.6 ohm
L7900 32 ohm
L7210 5.5 ohm
L7420 2.4 ohm
L7410 2.4 ohm
L7430 2.4 ohm
L7730 397 ohm
At first stage based also on graphic glitch before shut down described by the customer I thought was cpu fried but after I saw it booting once I have some hope for this board so I need some guidance.
Thanks in advance for any help.
I've seen what this community can do, so I'm pretty sure you guys can help me out.
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