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820-00165 CRAZY NO BACKLIGHT Issue

Bouba148

Bouba148

New member
Hi 2Informaticos; team

No Backlight
Tested with another known good screen : same
Display works fine on an external TV through a thunderbolt hdmi adapter

LCD not detected
Backlight flashes once when hearing chime

SMC not talking to the LCD:
SMBUS_SMC_0_S0_SDA and SMBUS_SMC_0_S0_SCL solid 3.3V

DP_INT_HPD: 2.67V in diode mode 0.460V

checked all capacitors and resitances on the LCD path

EDP_PANEL_PWR: 3.318V and solid just after the chime



As I've noticed that NO green light and NO keyboard
So I've suspected the SMC
Reflowed the SMC: same

Checked the bios with the Medusa, all the different parameters are looking fine and doesn't make me think about an SPI issue

I was OUT of Idea; so I took the other issues under consideration first, then I decided to check and focus on the green light
So I've disconnected the flex LIO board:
Backlight came back as well as the keyboard. CRAZY

Replaced both flex and LIO board: same

So wondering about USB issue shooting down the others signals
Plugged an USB mouse on the Motherboard USB port with the Flex disconnected : NO Activity

So now should I focus more on the USB Level or more on J9500?


Best Regards
 
2informaticos

2informaticos

Administrator
Staff member
"Replaced both flex and LIO board: same"
Looks like bad LIO connector (J9500) on the MLB.
Inspect it under microscope.
Check SMC_LID voltage w/ and w/o LIO flex connected.
If it goes down, TP/KB is disabled.
Be sure R5171 is OK.

Of course, do NOT use Magsafe adaptor 1-->2!!!
 
Bouba148

Bouba148

New member
Of course, do NOT use Magsafe adaptor 1-->2!!!:
YES SURE, I only une official 85W cables (magesafe 1 and 2 ) connected to Lab Power Supply

SMC_BC_ACOK: 3.387V
SYS_ONEWIRE: wave with peak to peak : 1.50V it should be 3.3V no?
Adapter sense: 1.5V also

Strange no? knowing that I already tried another Flex and LIO board.
What could create that drop of half of voltage....hummmm?

I'll try to run a wire directly from SYS_ONEWIRE of LIO to the test point near the SMC

Adapter Sense
Adapter sense.jpg

SYS_ONEWIRE:

SYS_ONEWIRE.jpg
 
2informaticos

2informaticos

Administrator
Staff member
If the signal (1-wire protocol) is the same on both lines, U6900 (from LIO board) works.
You must get aprox 3V DC on multimeter.

"Check SMC_LID voltage w/ and w/o LIO flex connected.
If it goes down, TP/KB is disabled.
Be sure R5171 is OK."
 
J

JohnB8812

New member
Replacing is not a bad idea. Those pins being corroded always causes issues make SURE the pins of the connector are soldered properly.
 
Bouba148

Bouba148

New member
Replaced LIO j9500 Connector: Problem Fixed

Backlight, Green/Orange Led, keyboard, Sound, USB Port ALL OK

Thanks 2Informaticos
You can set this topic as RESOLVED

Best Regards
 
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