820-3115 b

andrespi

Member
this macbook does not give video with a good screen, Could you tell me what measures to take initially, the fuse is good
 
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andrespi

Member
excuse me, it is other logic board problem.This logic board problem missing both image and backlight, not usb activity and not video external.This macbook turn on, fans Rotate normal, memory ram good, both slots ram memory is good
 
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2informaticos

Administrator
Staff member
How do you know RAM slots are good, if board doesn't boot?
Not always get classic beep errors, for RAM problems.

Do you have PLT_RESET_L high?
Any history fault available?
What is the CPU core voltage after 10s?
Did you try known good BIOS?
 
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andrespi

Member
PLT_RESET_L=3.3V
Any history fault available?NOT
What is the CPU core voltage after 10s?1.12V constant
Did you try knoen good BIOS?yes, the problem persists; whith chipmunk usb tester, only 5v usb,but no data usb
 

2informaticos

Administrator
Staff member
When board boots, VCORE should drop to 0.75V approx.
There may be a communication problem, because of bad PCH, or CPU.
Also possible to have bad trace, corroded, or knocked off resistor.
Check the series resistors from SPI lines and LPC bus.
 
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