820-00165 fan spins - no boot

Sykulski

Member
Got this one in saying no display. After reseating the battery the machine started. Ran for 24 hours. Next day it has shut off. I tried to start it again but now it is not booting. It has no liquid.

Symptoms are fan spins then stops then spins faster and faster.

VCORE is ok at 1.8V all the time

On first fan spin all pins on U6100 coming up. But when fan stops pin5 (SPI_MLB_IO0_MOSI) and pin6 (SPI_MLB_CLK) goes to 0V and don't come back on high when fans starts to spin again.

Where to start ??

Thanks
 

2informaticos

Administrator
Staff member
When board starts, these pins go low, is normal.
You can catch signal with o-scope.

Do you have 3V at pin 3 of U1950?
Check the MLB disconmecting LIO flex.
 

Sykulski

Member
OK. But shouldn't they come back high ?

I have 3.42V on pin3 of U1950
It is the same issue without LIO flex
 

2informaticos

Administrator
Staff member
Try the MLB, without any accessory; disconnect trackpad even.
Use only 5 pins DC cable from LIO.
Fan will go high, but you only want to see if MLB is booting.
Is better to use an OSX installed in a pendrive which has LED for control.
If LED flashes, board is OK.
 

Sykulski

Member
Board is not booting this way. Symptoms are the same

LED on pen drive with OSX installed lights up but no flashing (there is power but no activity)
 

2informaticos

Administrator
Staff member
Check all SPI termination resistors and traces around U6100.
Clean/remove J6100, if any corrosion sign there.
You can also try new BIOS...
 

Sykulski

Member
All termination resistors measure correct. Traces are good.
J6100 looks perfectly clean. Like new. There has not been any liquid (or even high humidity) near this machine.

Diode mode on U6100 pins with U6100 removed

1: 0.54
2: 0.59
3: 0.54
4: 0
5: 0.51
6: 0.51
7: 0.54
8: 0.39

Another U6100 is exactly same symptoms
 

Sykulski

Member
Actually it just came to life after i replaced the SMC (a panic action because i didn't know what was going on)

Now I need to let it run to see if some internal shit is now working because of heating up or it actually was SMC malfunctioning
 
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