820-00165 Works until you plug in battery

[bjf]

This came to us with the smallest amount of corrosion on C5126. I replaced that and U5110. Entire area around SMC, and entire rest of board, was clean. The computer works fine until you plug a battery in. After that the MagSafe light either stays orange or doesn't come on and the computer won't turn on. Any ideas? I'm not sure what would cause this.

 

[CRC2018]

Based upon the assumption you are trying a known good battery:
1) Check PPBUS Voltage is normal
2) check inside the battery connector on the board for any corroded pins - i've seen liquid move down the cable from the battery before and corrode the connector inside.
3) Check R5380, R5381 and R6950

 

[2informaticos]

"BMON is at 1.1V and then goes up to 8.59 if I keep the probe on it for a few seconds."
Are you sure?
CHGR_BMON should be lower than 0.5V without battery.
Now you get stable SMC_RESET_L?

 

[bjf]

Sorry, no, I was still looking at BGATE. BMON is at .63V without battery, and .50V with battery. And yes, I'm getting stable SMC_RESET_L now - with and without battery plugged in - ever since I measured 3V42 and it came back on. Something is unstable on this and appears to be intermittently failing. The liquid-damage was extremely minimal though so it's hard to know what's happening.

 

[2informaticos]

Try reballing SMC...

 

[bjf]

Any idea what would cause SMC_RESET_L to get pulled down like that? I had assumed U5110 but what you're thinking is that it was just the SMC doing it?

 

[2informaticos]

U7100, SMC and U5110 are connected there.
Corrosion at J6100 can also affect SMC_RESET_L.
Also voltages at pins 4, 6, 7 of U5110 are important; so components connected there should be checked too.

 

[bjf]

Thanks, I can't invest the time to reball the SMC but I changed everything around U5110, including a different U5110. We'll see if it holds up. If not I'll sell it as-is to someone who has time to pull the SMC.