[SOLVED]820-3190 liquid damage

[Cocobill]

Hello,

I got a 820-3190 with liquid damage that got under a RAM chip. Also got the beeps that confirm RAM issue. I ultrasoniced the board and now I don't even get a green light. I do have a board view file but no schematic...

 

[dukefawks]

The basics? 3V42? PPBUS?

 

[Cocobill]

Hello Duke,

PPDCIN_G3H 16.43V
PPBUS_G3H 0V
PP3V42_G3H 0.015V

 

[dukefawks]

PP3V42_G3H 0.015V, that is not good of course. Shorted?

 

[Cocobill]

Pin 1 of C6908 gives 106 KOhm resistance to ground

 

[dukefawks]

3V42 missing so the basics would be input voltage to U6990 on D6905 and inspect that area for damage.

 

[Cocobill]

D6905 gets no power... Power stops at Q6910. In my board view file Q6910 has 3 pins on the left and 1 on the right side. The actual chip has 4 top and 4 bottom legs...

 

[dukefawks]

Voltage on R6910 both sides and R6912?

 

[Cocobill]

R6910 pin1 16.43V pin2 16.27V, R6912 pin2 16.43V

 

[dukefawks]

R6910 pin 2 should be 6.8V as limited by the zener D6910. D6910 is dead or missing.

 

[Cocobill]

Thank you Duke, you're right. D6910 is missing. I do not have a doner board for this. Any other boards that have this component?

 

[dukefawks]

I believe all retina boards have the same input circuit.

 

[Cocobill]

D6910 was next to the MagSafe connector, so hard to replace... But it worked! Thank you Duke!!! Case closed