[SOLVED] 820-2936-B - water damage. no image

[Atomrepair]

Corrosion all over the place (see images).

Symptoms
I get a green light on the charger, machine switches on and fan starts spinning. After about 10 seconds, the fan speeds up to max RPM (heatsinks are in place)
If I have a stick of ram in the top slot, I get the gong to play, but no display (internal or external)
If I put a stick in the bottom ram slot, I get 3 beeps.

I checked the LVDS connector and, with the machine running, got no voltage on all the below pins:

PP3V3_LCDVDD_SW_F
PP3V3_S0_LCD_F
LVDS_DDC_CLK
LVDS_DDC_DATA
PPVOUT_SW_LCDBKLT
PPVOUT_SW_LCDBKLT

I looked at U9000 and noticed LCD_IG_PWR_EN is missing also.
Resistance from LCD_IG_PWR_EN to ground is 88 kOhms
LCD_IG_PWR_EN comes from U1800, not sure how to proceed from here.

 

[Atomrepair]

update:

Just noticed that J5800 has two blackened pins; 19 and 21.
21 has no voltage, should be PP18V5_S5.
19 has SMBUS_SMC_A_S3_SCL = 3.3V, which I assume to be okay.

I looked at PP18V5_S5, it starts at U5805 as PP18V5_S5_FB

U5805 has nothing on pins 1, 4, 5 and 8.
Pin2 (PP5V_S5) = 5.02V

replaced U5805 - no change

 

[dukefawks]

Obviously the LCD connector is totally fucked for a start, LP8550 looks pretty sad too.
PP3V3_S0_LCD_F should be present as it is connected straight to 3v3_s0 through L9008, check L9008 and traces.
LCD cable is probably fried also if the connector looks that bad.

 

[Atomrepair]

I've replaced the LVDS connector and LP8550. Tested it with a functional screen and cable, screen works!
The LVDS cable in the water damaged mac actually looked clean, so I decided to risk it and try it in the case it came out of, and it works too.
Ram slots are working fine too, turns out it was a bad ram stick which worked 'sometimes'.

This is only my third logic board repair (I've only done 'windows' laptops before) so I'm stoked!
Thanks, Duke!