[solved] 820-2936 randomly turning off after liquid

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Active member
Hello all,

my first post,

i have a 820-2936 board, had no green light when it came in, fixed the PP3V42_G3H
green light and fan spin

but now it runs and i get a nice dong after that i can use the pre-installed hdd whit os. or i can run ASD.
full PASSED message and everything is smooth i thought.

here is the issue, it randomly turns off, or the screen goes black, back on, black and back on again

tonight if wanted i can upload the movie i recorded. not mutch to see thou



Staff member
Define exactly what you originally repaired here, and what the original damage was.

Ripple on PP3V42_G3H will be most damaging to the SMC. In machines prior to core i5/i7, ripple on PP3V42_G3H would be most damaging to MCP clock circuit and the SMC. So my only guess is something SMC related, or corrosion that you missed if this was originally liquid damage.

Our job is not to be psychic, but rather to be detectives. We figure out what is wrong based on original issue, and what the board tells us. There's a story there you need to beat out of the board and convey in your post to get to the root of your problem!


Active member
waterdamage around u7000, and a drop around U6901

bad u6901 not getting pp3v42_g3h replaced it and that was oke.
u7000 had no 4v on acin, u7000 was not looking bad but after replacing it, it was good.

i dont remember if there was a ripple on pp3v42_g3h, (LESSON 1 write every step and thing even if you think its good so you can Always go back)

i did not clean the board yet but the smc U4900 looks clean. (under the micrscope.)

today i took out the board, to check for waterdamage, after putting it back and pluging in the charger i got nothing. no green light no fan nothing,

i took my multimeter on volts, and measured pp3v42_G3h. at the moment i touch the probe next to u7000 pin 1 probe 422 R7002 i got green light and it booted.
after the boot again the screen went black. and back on again and off.


Does it completely shut down or does it go into sleep mode? The screen on/off thing makes me suspect it goes into sleep mode.
The no green light issue could very well be that there is corrosion under the SMC. Put some flux under it and heat it up to 150C, don't melt the solder just apply some good heat to clear the crap under it.
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Active member
fluxed the smc 150C heating

it stays on just the screen goes off, but hybernating looks the same

after that booted and ran ASD, now tobad it gave a SMC error this round... so atleast the heating worked :)

so best bet replacing the SMC, anything to watch out for before replacing it ? not that something else burns it when i replaced it..

oke rebooted ran test again (wanted to write the exact error code)
now i get a new error,

Error _ Random Multi block test failed

running again reboot

after the reboot,

ERROR - SMC IO failed

measured the probe 422 gave a smooth 3,419 or 3,418
but when i took away the probes the system shut down.

unplugged, resistance. red on ground, black on probe 422 gave a 0.462 stable.

measured whit osciliscope, no green light, 3,4 v.
when i then measure whit multimeter, green light turns on and dong......

then measure again whit osciliscope green light stays on and 3,4 v stable,

when i then take the multimeter and want to measure on probe 422 again the system turns off, green light stays on.
whit osciloscope i get 3,4v stil stable................
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You are writing a bunch of things that are missing context. Block test is a failing harddrive. SMC IO should contain a specific sensor(s).


Active member
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thought i was missing something, i wrote all that was in red thou.

the block test was because of a harddisk not compatible whit the macbook, after i changed it i didnt get that message.

the SMC IO i changed the SMC meanwhile.
running the ASD test, taking alot longer now but passed the before errors, also no signs of turning off the screen yet.

got this now.

PASSED. :) makes me happy.and no tunring off from screen for 2 hours, before it happend every max 5 minutes


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Any SATA drive will work. That HDD is just bad, run a full block scan and you will see. Good news on the SMC replacement!
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