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820-00164: Wont power up when pwr button pressed

M

macRepairAmb

Member
Hello gents.

Have a weird one.

Original Issue: Wont power up not was MagSafe light on. corrosion around SMC. Replaced all corroded capacitor and resistors along with SMC chip (due to short seen on Couple of caps).

Repaired and board now boots up.

New Weird issue: can?t power up the computer using the power button. However, I can perform SMC reset, power off the computer by holding down on the power button. I power on the computer when MagSafe is connected right after reconnecting battery.
 
M

macRepairAmb

Member
I think I may have figured out what may be wrong. I?ve got 3.4v on smc_onoff and 0.4v when power button is pressed. Going to pull the SMC and check for continuity.
 
J

JohnB8812

New member
That's normal pressing the power button shorts SMC_ONOFF_L to ground....have you tried a known good keyboard, trackpad, and trackpad flex???
 
M

macRepairAmb

Member
I currently do not have a keyboard/trackpad parts for the model to test with (i checked and ohmed out the ribbon cable from the trackpad to the logic board, just incase there were bridge connections, and it ohmed good). What i'm wondering is, if it was either of these guys, would the power button still respond when i press it to shutdown the computer? Plus from the smc_onoff voltage drop when i press the power button, it appears the keyboard may be working as well. Why i was thinking of going for the smc is due to having 3.4v present, which is fed from what i believe is a pull up resistor (R5170). Since this voltage is present, i'm thinking the trace from that resistor to the smc must have corroded away.
 
M

macRepairAmb

Member
Before i pull the smc, i'm curious what the resistance measurement on smc_onoff_L should be. I'm getting about 144K, does that sound about right. Its the exact same measurement i'm getting on a donor board that's missing its smc.
 
J

JohnB8812

New member
Try a KNOWN GOOD trackpad and trackpad flex first do not blindly replace the SMC when it could be something super simple....you NEED to stock these test parts anyways if you are going to do board repair.
 
2informaticos

2informaticos

Administrator
Staff member
"I can perform SMC reset, power off the computer by holding down on the power button"
So SMC receives the power button signal!

Check if PM_PWRBTN_L reacts when you trigger SMC_ONOFF_L signal, for a short time.
 
M

macRepairAmb

Member
Weird, so i soldered a test wire to J1800 (XDP_CPU_PWRBTN_L) since it was tied to R1082 (0ohms). Power the laptop up to test and now i can't keep it powered off. It just keeps restarting itself after I power down the board. I even unplugged the keyboard and it still powers itself back up after i power it down. I confirmed the wire i installed was bridged across another pad and then also pulled the wire with the same result. I had noticed this issue earlier today but it went away, so thought it was a fluke
 
2informaticos

2informaticos

Administrator
Staff member
"i soldered a test wire to J1800 (XDP_CPU_PWRBTN_L)"
WHAT???
I asked you to do something different.

BTW, I cannot find R1082 on 00164 board; you meant R1802, I suppose...
 
M

macRepairAmb

Member
So any suggestions? Its reads 3.325v each time i press the power button with no spikes or sudden drop. Plus the board keeps powering itself back up after i hold the power button long enough for it to shutdown.

After allowing it to bootup completely into OS, and then shut it down, it now stays shutoff and the power button doesn't respond unless i unplug and plug the MagSafe before the board powers up again. Also, PM_PWRBTN_L still remains at 3.3v when i attempted to power it back up with the power button this time around.
 
2informaticos

2informaticos

Administrator
Staff member
Now try triggering PM_PWRBTN_L instead.
Board should start.
Touch the ground with previously wire soldered on R1802 for that.
 
M

macRepairAmb

Member
Yep the board starts and i can also shut it down with the same wire to ground and it stays shutdown after i take the wire off ground.
 
2informaticos

2informaticos

Administrator
Staff member
Normal, because SMC is not informed about pressing power button.
You issue is SMC related.
Normally should change the SSMC and check if all its pad are OK.
Another trick is soldering a diode with the anode on PM_PWRBTN_L and cathode on SMC_ONOFF_L.
Just for test, I'm not sure if timing requirement for power on is OK in this case.
 
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