820-2936-A no green light

[Mario Mancari]

I bought a macbook with 2936A without green light.
The old owner says he saw smoke from chargers.
-F6905 OK but dc in is 6.80v
-3.42v ok
-ppbus nothing
-U7000 replaced and checked all nearby resistors. Still nothing fixed.
U7000 Pin: 17/18 = 1.1ohm 27/28 = 20.2ohm
r7010 pin 1 = 6.80v / pin 2 = 1.5v r7011 pin 1 = 1.5v / pin 2 = 0v
-F7040 = ok

 

[2informaticos]

Replace DCIN board.
Try another charger, fake one even.
Also test with lab PSU...

 

[Mario Mancari]

power jack dc when unplugged from the board generates 17v. when i connect it to the board it drops to 6.80v.
I buy it anyway. The charger is new

 

[Mario Mancari]

After powering the board with 16v L9004 exploded

 

[2informaticos]

Test the board alone on the desk.
What is the actual state of the board?

"power jack dc when unplugged from the board generates 17v"
Because that is fake charger.

 

[Mario Mancari]

i am already testing the motherboard on the bench. only the cooling fan is connected.
Now the board is with L9004 exploded and I will replace it as soon as possible.

 

[Mario Mancari]

Why did L9004 explode? problem in the rail?
now i have 0v with the charger connected

 

[2informaticos]

L9004 can get burnt if a short to ground is present on its output.

 

[Mario Mancari]

can this short be the cause of the no power and no green light?

Advice on what to check to eliminate the short?

Thank you!

 

[2informaticos]

Can cause such problem only if U9000 is bad too.
Remove U9000 and test the board.
Once you get USB activity, then go for image too.

 

[Mario Mancari]

Replaced L9004, u9000. The few 6.5v on DCIN are back. i noticed pin 2 and pin3 of j9000 shorted. checked c9015, c9012, c9011 and unplugged u9000 but remains shorted. could be the cause of the little dcin? Could it be video card?
I bought a new board work and the display works
Power jack dcin Replaced

 

[2informaticos]

"i noticed pin 2 and pin3 of j9000 shorted"
Good enough, did you see schematic?

"The few 6.5v on DCIN are back"
Test with lab PSU and fake charger.
Possibly leakage issue on input stage.

 

[Mario Mancari]

Sorry
pin 1 and pin2 j9000 shorted to ground

 

[2informaticos]

Check that disconnecting video cable.

 

[Mario Mancari]

All disconnected. Only the connected fan

 

[2informaticos]

So the short is inside board, or LCD connector.
Now remove L9004 and see where the short remains.