820-00165-a fan spin, no chime, no display

[jakenz]

Liquid spill, corrosion around u6100, everywhere else looks perfect.
Originally no boot, after removing u6100, cleaning pin 7 and replacing, it turns on, has vcore, gets warm, fan spins normally, will turn on and off with power button.
No chime no display, no backlight

u6100 replaced from donor board - twice.
diode mode with u6100 removed is
1-0.609
2-0.450
3-0.515
4-0.000
5-0.389
6-0.518
7-0.475
8-0.475

so far i have replaced u6101 and u1900. removed j6100

Not sure where to go from here.

 

[arghhh]

USB mouse light up?

 

[jakenz]

No, nothing at all.

 

[arghhh]

Voltage on pin 8 of U6100 and PPVCC_S0_CPU?

 

[jakenz]

u6100 pin 8 3.342v, ppvcc_s0_cpu 1.802v

 

[dukefawks]

Where did you take U6100 from? You cannot just change them between boards, put back original.

 

[jakenz]

Originally i replaced the same chip after cleaning pin 7, when that had the result i described above i replaced with another from the same model 820-00165-a donor. Same result

 

[dukefawks]

At least put back original chip and check all resistors in serie with data lines R6110 and up 18 of them. Also the traces between them.

 

[jakenz]

Replaced original u6100, checked all resistors between r6110 and r6133, all fine, traces between them have 0.000v voltage drop along them, only traces to smc and cpu i could not measure

 

[dukefawks]

Pin 8 of U1950 corroded? Was there crap around U1900?

 

[jakenz]

pulled and checked u1950, looks fine, liquid didn't look to make it as far as u1900 but i pulled and replaced anyway.

 

[dukefawks]

Out of ideas. Check all resistors and traces to U6100 again, there are 20 or so of them in that circuit.