820-00165 No boot sometimes

[javier_herart]

Hello.

2 Months ago I received this board with liquid damage around U3210 and U8020. I reflowed and cleaned the area and it worked fine for 2 months.
It came back today, sometimes turns on with no problem and sometimes wont boot (no video and no caps lock). No signs of new liquid damage. Any advice?

When no booting and no video:
ALL_SYS_PWRGD: 3.3V
PPVCC_S0_CPU: 1.8V
PLT_RESET_L: 3.3V

 

[2informaticos]

Something was affected by corrosion in time.
Possibly accumulated crap under BGA chips.
Did you reball SMC?

 

[javier_herart]

Should I take it to the ultrasonic cleaner?

I reflowed the SMC but no change.

 

[2informaticos]

Don't waste time with reflow.
Always reball SMC, for corroded boards.

 

[javier_herart]

I reballed the SMC and cleaned with ulstrasonica cleaner and same.

Any idea? Try another smc?

 

[2informaticos]

If thunderbolt is not needed, remove Q3080 and test the board again.

 

[javier_herart]

Removed q3080 and same, turn on but no video

 

[javier_herart]

Tried another SMC and same. Any idea?

 

[javier_herart]

MEASUREMENTS
WITH OTHER SMC,
TURNS ON AND NO VIDEO,
NO BLOQ MAYUS,
IT TAKES 600 mA and then only 450mA (Known good boards take 700-800 mA when booting ok with screen connected)

-SMC_LID: 3.42V
-ALL_SYS_PWRGD:3.4V
-PLT_RESET_L: 3.4V

-CPU_VCCST_PWRGD: 1V
-CPU_VR_READY: 1V

Still sometimes turn on and shows the folder. ( 1 time of 20)

• Could be bad solder right?
• I already reballed (and changed) U5000.
• If i get the measurement above can I assume that the RAM chips are ok? What could I measure?
• Should I reflow CPU?

I tried another bios and same issue

 

[javier_herart]

I noticed that when CPU is cold the MB turns on and shows the folder, but if a disconnect and connect (after it shows the folder) then it wont boot/show the folder.
When I leave the motherboard with no power for 2-3 mins and connect again it shows the folder.


SMC_PROCHOT: 3.3V when MB wont boot/show folder
SMC_PROCHOT: 0 when machine boots/shows folder


Any idea?

 

[2informaticos]

Check if starts in SMC bypass mode.
Also try removing Q5159.

 

[javier_herart]

Same issue with SMA bypass.

Removed Q5159 and same issue.

Same behaviour, I let the board "rest" for 3 mins and it boots/shows the folder.

 

[2informaticos]

Possibly accumulated crap under PCH/CPU...

 

[javier_herart]

I first tried with reflow on CPU and the Board wont boot anymore.

I reballed the CPU and it seems the board is working ok now, I need to test it in detail.

The only think I notice is that the FAN is running fast. (I tested only on the bench)

So far its been a good progress I guess

Gracias!

 

[2informaticos]

Trackpad must be connected.
If not, the fan goes to max speed.

 

[javier_herart]

macbook fixed