a1707 820-00281-a no backlight

N

Nicus009

New Member
Hi all,
I have a macbook a1707 with a board 820-00281-a. The screen backlight does not work. I first replaced the capacitor after the d8410 diode. The voltage rose to 10-12v. , the backlight does not shine. There is still no voltage on ISIS_LCDBKLT_P, although there is a voltage of about 11 volts on ISIS_LCDBKLT_N.
Can you tell me how to solve this problem with the backlight.
I am attaching a photo with notes on the voltage at the backlight control area.
 
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It's a boost regulator circuit; IF the CPU is enabling the backlight and the controller IC U8400 is OK, you should see a logic-level PWM drive signal on pin 4 of that, feeding through to the gate of Q8401

If there is no drive signal, either the IC is dead, not being commanded on from the CPU, or is sensing a fault, eg. such as excess current (from the voltage across R8400).
 
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No,if i remember i just try only one combination on keyboard,i'll try this
If it helps,i'll reply
Thanks
 
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