820-3787 Fan goes high and laggish after 10 secs. Left Fin Stack Proximity failed in ASD test

[Mac Repairs]

Hi all,

This is not a liquid dmg board.
Fan goes high and laggish. ASD test failed with Left Fin Stack Proximity.

SMBUS_SMC_0_S0_SDA AND SCL CLEAR 3.3V. GPUTHMSNS_THM_L IS 3.3V.

Missing GPUTHMSNS_ALERT_L. 0V.
I replaced Q5801,Q5803, U5850 still no luck. DATA sheet says it requirs a pull up resistor to get the voltage.

Any idea?

 

[2informaticos]

Try first disconnecting webcam.

 

[Mac Repairs]

I did. No webcam, No wifi. Replaced the SMC same issue.

 

[2informaticos]

Check traces from Q5801/03 to U5850.

 

[Mac Repairs]

connectivity between Q5801, Q5803, C5852 are present. Diode mode I get around 0.6XX V. voltage on C5852 i get 0.5v on ipin 1 and 0.1v in pin 2.

 

[Mac Repairs]

I already replaced the C5852 still no luck.

 

[2informaticos]

Check voltage and diode mode on SCL/SDA lines of U5850.
Also test the machine removing U5850.

 

[Mac Repairs]

SCL/SDA Voltage is 3.3V. Diode 0.652V both lines. Remove U5850 I get missing GPUTHMSNS_ALERT_L. 3.3v.

 

[Mac Repairs]

removing U5850 still fan high.

 

[2informaticos]

What errors appear on ASD, running without U5850?

 

[Mac Repairs]

ASD FAILED WITH OUT U5850 and those are,
(TG0D)- GPU-Die Anolong (test 1)
(TG0P-GPU Proximity
(Th1H) Right FinStack
(Th2H) Left Fin Stack

Other than these 4 all passed.

 

[Mac Repairs]

With U5850 Only (Th2H0 Left Fin Stack Failed.

 

[Mac Repairs]

I mean (Th2H)

 

[2informaticos]

So U5850 works and it only receives bad signal from Q5801.
Interchange Q5801/03 and see what happens.

 

[Mac Repairs]

Interchange Q5801/03 no lcuk. Replaced again Q5801/03/C5852. Still no luck. Removing Q5801/03 I get 1.5V in Q5803 pic1,3.

 

[2informaticos]

When interchanged transistors, same sensor error reported?

 

[Mac Repairs]

wiredly yes. And thats why i replace both Q5801/03. still same left fin stack failed.

 

[Mac Repairs]

I checked the connectivity again between Q5801/03/U 5850, C5852 and they are all connected.

 

[Mac Repairs]

And still missing missing GPUTHMSNS_ALERT_L.

 

[Mac Repairs]

Also U5850 Pin 4, I get 0.4 to 0.5V and pin 5 0.124v