820-00165-A Not display on int or ext screen. Orange light and fan spins,

[joshAU]

Hi all.
I have a water damaged 820-00165-A that has no display, either on the internal panel, or on an external screen.

There is zero change on the screen when power is connected.
I cannot see an Apple logo or folder question mark while shining a light from the back.
I have tried another replacement panel, and on an external monitor, with the panel disconnected.
Tried with two known AC adaptors.

There is no chime.
The fan comes on, the Magsafe light starts green, then turns and stays orange.
I have tested the board out of the chassis, with only the Magsafe2 connector, and ext monitor connected.

The water damage was visible on and around the WLAN card, and on the opposite side of the board.
(For example, close to U7400)

PPBUS_B3H 8.0v
PP3V42 = 3.41v
SMC_LID = 3.42v
SMC_RESET_L = 3.39v
ALLSYS_POWRGD = 3.3v
PPVCC_S0 = 1.05v
PP5V_SO -= 5.1v

If I plug in a USB drive, the light on the USB drive comes on, but stays solid, instead of showing activity.

Suggestions appreciated.
Thank you.

 

[gir489]

This sounds like a question for Louis and he doesn't frequent the forums enough to answer you. I'd see if you can call the shop and ask him personally, although it's pretty hard to get him on the horn.

 

[2informaticos]

Don't watse time searching for video, if no USB activity detected.

Please, post exact PPBUS_G3H voltage (without battery); 8.2V is not the same as 8.5V and 8V mentioned is irrelevant.
Do you get PLT_RESET_L?

 

[joshAU]

Thanks 2informaticos.
Sorry, i had tested video prior to checking if there was USB activity. I guess its easier to go the other way.
Still learning.

I was also rushed yesterday, so apologies for the typos... PPBUS_G3H is 8.56v.
PLT_RESET_L = 3.31v

 

[2informaticos]

Check all SPI Bus Series Termination resistors and their traces.
Clean J6100 and inspect U6100/01 for corrosion.

 

[joshAU]

OK.
Cleaned J6100 - was a tiny residue of crap still there surprisingly, but no change.
Cleaned both U6100 and U6101 - no change.

Checked voltages on SPI Bus Series Termination resistors.

SPI_SMC_MISO 3.31v (measured at pin 2 of R6114)
SPI_SMC_MOSI 0v (measured at pin 2 of R6115)
SPI_SMC_CLK 0v (measured at pin 2 of R6116)
SPI_SMC_CS_L 3.31v (measured at pin 2 of R6117)

I checked resistance to ground on MOSI and CLK:
MOSI 623 Ω (measured at pin 2 of R6115)
CLK 560 Ω (measured at pin 2 of R6116)

I then went through and measured the resistance across all 22 SPI resistors.
All matched their values.

I assume the MOSI and CLK should not be zero volts?

 

[2informaticos]

"I assume the MOSI and CLK should not be zero volts?"
Wrong assumption; is exactly as should be.
When have such doubts, just check working board on similar points.

Did you really remove U6100/01 and check their pads underneath?

"I then went through and measured the resistance across all 22 SPI resistors."
What about connection traces between them?

J6100 may need to be removed.
Just in case, try known good BIOS; corrupted BIOS was sometimes reported in case of liquid damage.