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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."
 
Bouba148

Bouba148

New member
I've forgot to mention that I saw minor corrosion at J9500 between pin4 and 10, that of course I've cleaned and quickly re heated.
Maybe invisible crap under it... Will pass it in the UC, if not successfull replace J9500.
What do you think ?
 
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.
 
2informaticos

2informaticos

Administrator
Staff member
If is only one line problem (like SMC_LID), you can cut it off from J9500 and bypass with direct wire between MLB and LIO board.
 
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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