820-4924 Only powers on after a long press of power button

[No-Clean]

Clean board, had some work done near keyboard connector somewhere else, checked all that work and everything is fine.

Problem is that when board is connected to power for first time it tries to turn on but shuts down right away, board will start fine after pressing and holding power button or shorting SMC_ONOFF_L for a few seconds usually more than 5 seconds, even then not all the time it starts but most of the times it will.

So far I have tried clean ME BIOS, new SMC, new U7100 and new U5110 but same exact thing.

U5110 Pin 1-3 3.3v pin 5 3.3v

PPBUS when board is off 12.56v

Diode mode on SMC_ONOFF_L is on par with working board, same with pins 1-3-5 of U5110 all measure fine

 

[2informaticos]

Looks like your board only boots in SMC bypass mode.
Check resistance between pins 17/18 and 27/28 of U7100.

 

[No-Clean]

I checked those before and they are fine 17/18 4.3Ω and 27/28 20.9Ω

 

[2informaticos]

Check SMC_DCIN/PBUS_VSENSE and SMC_DCIN/BMON_ISENSE.

 

[No-Clean]

They are on par as far as diode mode reading, but when board is off and connected to power SMC_DCIN_VSENSE is 2.4v and all the others are 0v.

 

[2informaticos]

Aaaa, board tries to start in normal mode, but shuts down fast.
Then must be another SMC sensor issue; check pages 42-44.

 

[No-Clean]

Ok this board end up back in our place again and I will like to fix it this time.

Already checked all sensors in pages 42-43-44 they all look fine and measured correct.

When I plug the board to power I can see the amps go up then they come down and board shuts down.

If I short smc_on for about 5 seconds board boots in what I assume is smc bypass.

Board looks clean and it looks like some work was done on the keyboard connector, pins 1-5 have wires/bridges but I already checked that and all that is working fine, in fact this board was used for a while after the keyboard connector was fixed.

 

[2informaticos]

Is SMC_ONOFF_L steady high?
Just in case, remove C4810.
Does the board start normal removing keyboard flex?
Use R5115/16 pads, instead of power button.

Is the battery recognized and charging?

 

[No-Clean]

SMC_ONOFF_L is steady high at 3.4V
Board alone tries to boot, I can see in the PS, but it shoots down shortly after and only a long press/short on SMC_ONOFF_L will turn it on

Battery is recognized and charge is fine.

 

[2informaticos]

There is clearly SMC sensor issue, if only starts in SMC bypass mode.
Is AVREF_SMC present?

 

[No-Clean]

C5125 was shorted on that line PP3V3_S5_AVREF_SMC

You are a mastermind, thanks a lot, if you lived near by I would buy you a beer!

 

[2informaticos]

Glad to hear is solved.

Man, I live faraway of Paradise .
Actually Madrid looks more like a Hell...