820-00138 can't power on or off on keyboard or power pads

[zockysworkshop]

it goes down to 0.8v at the connector

 

[dukefawks]

Do some resistance measurements on the different points where you can get to SMC_ONOFF to the KBD connector pin.

 

[zockysworkshop]

PP3V42_G3H is short to ground i measure in diode mode on pin 1 on R5170 I get 0.7 and measure on pin 2 i get 0.068. Any ideas what to do ?

 

[dukefawks]

I don't see how the board could even work like that. Are you measuring with power applied?

 

[zockysworkshop]

I don't have bench power supply to inject voltage

 

[dukefawks]

Read my question again....

 

[zockysworkshop]

I measure no power applied i wonder also how the board also working

 

[dukefawks]

With 0.06 Ohms on 3V42 there is no way this board work. Go and check again.

 

[zockysworkshop]

I checked 3 times in diode mode the red probe on ground and measure with 2 different multimeters same result. I'm really confused

 

[dukefawks]

Well something must get warm with such a low resistance. Feel around the board, SMC would be a good suspect.

I still don't see how the board can work. If resistance to GND on 3V42 is 0.06 Ohms then the current would be 3.42/0.06=57A!

Is the battery and AC really disconnected when measuring this?

Also check resistance to GND on L7095

 

[zockysworkshop]

Everything is disconnected no power no battery and on L7095 resistance was same. So i got power supply from old desktop computer and i inject 3.3v and didn't change anything and after i inject 5v and after that was showing me 0.2 resistance but now dropped to 0.1 resistance and the board is still turning to OS

 

[dukefawks]

You inject 5V on a 3.4V bus? Please, what the hell are you doing??

I have no idea what you are doing anymore. If you inject 3.3V on a 0.1 Ohm short something will start getting hot.

 

[zockysworkshop]

i injected 3.3v on PP3V42 nothing was hot after that i injected 5v on same rail PP3v42 and the resistance from 0.06 went up to 0.1

 

[dukefawks]

Let me do some Ohms law for you. I=U/R, I=3.3/0.1=33Amps. I'm curious to see what power supply you are using that supplies 33A. Also smoke should be coming from somewhere and there is NO WAY this board can even have a green light. P=U*I P=3.3*33=109W. Something must be dissipating 109W which is some serious heat!
I have no idea what you are measuring or doing so I can't give any more advice at this point. Is this board even working at this point?

 

[zockysworkshop]

The board is working fine just no power button and no keyboard