820-3476 - Unstable and locking up after water damage

Mattpd

Member
I have a 829-3476 that came in mostly dead. Charger light would turn green then orange, but would never turn on. Checked voltages and found all of them present except for CPU_VCORE.

Examined board and found a tiny bit or corrosion around U7600 and U8330. Cleaned it off then ultrasonic bath. CPU_VCORE is back and the macbook is able to turn on.

It will turn on, chime, and boot with no problem. It's not until you try to login does it give issues... Here are a few situations that I noticed:

If I try to boot with everything connected (touchpad included) it will get to the user selection screen. When you select a user, it will lock up, beachball, sometimes flash graphics glitches (checkboard pattern). Sometimes it will take you back to the user login screen, and sometimes it will just lock up hard.

If I try to login while it's in cripple mode (touchpad unplugged) it will actually work. It runs slow as hell, but I can login, get on Safari and play a youtube video.

If I plug everything back in, including TP, and boot into safe mode, it works great. No slowness, or locking up. I get the occasional screen flash when scrolling web pages, but that may just be because I am in safe mode...

It passes EFI ASD with no errors, with everything plugged in.

It won't load the OS ASD with the TP plugged in. It tries to load, says "finding available tests" eventually lock up and turn black, and then go back to "finding available tests"

I have already replaced the whole top case also.
 

dukefawks

Administrator
Sounds like a RAM issue to me. Corrosion under RAM or CPU. Run ASD EFI version and see if RAM gives any errors.
 

dukefawks

Administrator
It could really be corrosion anywhere. Inspect all affected areas for damaged traces or resistors. Could be crap under a pin of U7600. Put some flux and heat on the areas that were affected, don't reflow just some heat to clear the possible crap under the chips.
 

Mattpd

Member
Replaced C8340 even though it was measuring the correct value with no short, it was just slightly corroded. Everything seems to be working fine now. Does that make any sense or did I just get lucky?
 
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Gurmon

Member
Replaced C8340 even though it was measuring the correct value with no short, it was just slightly corroded. Everything seems to be working fine now. Does that make any sense or did I just get lucky?

Who knows..... Keep unit on test for a period of time to see if issue returns. Sadly luck has seldom helped me in fixing boards :-(
 

Mattpd

Member
This stupid thing...

It works much much better, but it still screwing up sometimes.

I was able to login and play youtube videos for hours straight last night.

Today, it doing something similar to before. It will randomly lock up and send you back to the login screen.

System log has a bunch of "GPU Reset" events:

Intel GPU Hang Summary
MAIN Ring is hung it batch buffer <--- ROOT CAUSE! (Some of the errors says "is hung in the ring")
MEDIA Ring is idle
BLT Ring is idle
VEBOX Ring is idle
 
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