820-2850 Can't turn on after shut down.

[Don Anton]

Hi all,
This came with no any liquid damage.

But broken cap C5725. initial issue is can't turn of after shutdown. Power Button works time to time. . power on when connect the charger and can shutdown pressing power button but can't turn on again.
When this happen can't turn on even shorting power pads. Replaced C5725 same be behaviour. disconnecting keyboard, pressing power pads it stops and restart.

Checked with known woring keyboard same issue.

SMC_ONOFF_L 3.3v and pressing power button does to 0.4 for few seconds and back to 3.3v SMC_RESET_L 3.V, SMC_LID 3.3v and BUTTON_DISABLE 0V. R5710 and C5710 get 3.3v

I HAVE REPLACED C5725, U5725, SMC But no luck.


Any idea?

 

[2informaticos]

Post the 4 RTC signals...

 

[Don Anton]

Here are the RTC rails.
RTC_RESET_L:3.3V
PCH_SRTCRST_L: 3.3V
PCH_INTRUDER_L:3.0V
PCH_INTVRMEN: 3.3V

Once shutdown from the power button. only can start by disconnect and connecting the charger. once boot all the keys are functioning.

 

[2informaticos]

Try the board alone on the desk; nothing connected, apart of an USB mouse.
Check if you can turn it off and on using power pads R5015/16.

 

[Don Anton]

board alone on the desk shrting power pads can turn on and when turn off it restarts my itself.

 

[2informaticos]

If maintain SMC_ONOFF_L low for 4-5s, remains off?

 

[Don Anton]

When shorted the power pads SMC_ONOFF_L is low after relaese power pads back to 3.3v and fan spins again.is this normal?

 

[2informaticos]

I asked what happens if you keep SMC_ONOFF_L tied to ground 4-5 seconds...

 

[Don Anton]

oh sorry, as long as SMC_ONOFF tied to ground , power drops and remain 0.01mv and fan stop when you release after 2,3 seconds it boots by itself. all this happen board out on the desk, connecting charger and usb mouse only. when it boots back on the machine it works fine and boot the osx and can shut down by osx or pressing the power button. but can't turn on again unless connect the charger and tuto boot.

 

[2informaticos]

When the board is in the case, remove the keyboard and see if you can turn on with power pads; after shut it down from OSX.

 

[Don Anton]

once shutdown from the OSX, removed keyboard and tried to on with pads not working. only wayto turn on is reconnect the charger

 

[2informaticos]

Do you note a drop pulse at PM_PWRBTN_L when trigger SMC_ONOFF_L?

 

[Don Anton]

Hi Info2 this is SOLVED. R5710 was accurate. But as a last option i replaced R5710 and C5710. all good. Thank you again for your help.

 

[2informaticos]

R5710 shouldn't void power pads from MLB to work correctly.
I suppose C5710 had leakage...

 

[Don Anton]

Ok. Good to know that. But its hard to diagnose. Anyway thank you so much.