820-00239 turns on but no fan spin/nothing on screen

[ytesfay80]

This board was sent to me a few weeks ago not turning on with liquid damage from UB400 down to the C9344 area. I replaced all of the damaged components in those areas except for UB400 and ultrasonic'd the board. It worked perfectly fine after that and it worked for a couple of weeks before the customer sent it back to me saying it doesn't turn on anymore.

When I plug the charger in I feel the heatsink getting warm and the trackpad clicks when I press it but the fan doesn't turn on and nothing appears on the screen. I have tried an SMC reset and unplugged the battery power but that still didn't fix it.

I'm not sure what power rails to start measuring to solve this. Has anyone had this issue?

 

[2informaticos]

Do you get voltage at all coils?
I'm reffering to all secondary power supplies.

Check for USB activity and external video.
Liquid spill at LCD connector?
Check between pins 1 & 43 for any sign of liquid.
This could fried the LCD output of CPU...

 

[ytesfay80]

I'm not sure what the secondary power supplies are so I measured all of the coils on the top of the board.
Here is a list of the coils that got no voltage on them
LB700, L7030, L8410, L3500, L7410, L7420 and L7430

I plugged in a usb stick and that showed as having power. I can't find my hdmi adapter so I can't the external video output today.
There wasn't any liquid damage around the lcd area and the area looks fine.
I did forget to mention that the liquid damage was on the keyboard and the keyboard is still sticky even now. The customer told me to leave the keyboard as it was and they will get it replaced at a later time.
I believe I read somewhere that the keyboard and fan are connected so could that be why the fan isn't turning on anymore?
Also, I'm not even getting a chime like I was when I initially fixed this board.

 

[2informaticos]

Does the board turn on if keyboard is removed?
Any voltage at F7000?
Check at R7020 too; post the exact value there.

Possibly issue related with USB-C controllers...

 

[ytesfay80]

So something unusual happened. I went back to check the fuses you asked for and as soon as I opened the lid I saw the backlight on the screen and after a few seconds the questionmark folder appeared. I shut it down using the power button(this is a touchbar) and turned it on again but nothing shows up on the screen anymore. It did it again one more time and I even heard that other chime noise it makes but I'm not sure what I did.

The board still turns on with the keyboard unplugged but nothing appears on the screen. The fan works though because I unplugged the trackpad cable and turned the machine on and the fans turned on right away.

I measured F7000 when I plug the charger in it gives me around 11.6v and slowly goes up to 12.25v.
R7020 gave me 19.82v on pins 2/4 and 19.85v on pins 1/3.

 

[2informaticos]

Check SMC_LID voltage...

 

[ytesfay80]

I opened the macbook and hit the power button and the screen turned on and booted to the question mark folder again. I turned it off and on again but it went back to no screen activity.

SMC_LID is a steady 3.41v

I'm not sure why it boots to a questionmark folder. When I initially fixed this it did that questionmark folder but once I cleaned up and replaced the damaged components near the SSD area(replaced U5860, C9334/40/44/45, C9201/14/15/20) it booted to the correct login screen.

 

[2informaticos]

SMC_LID still high when no screen?
Check voltage and signals at J9600; do not disconnect it.

Also start with USB OSX and check if internal SSD is recognized in Disk Utility.

 

[ytesfay80]

Yes. SMC_LID stays 3.41 with the lid open and nothing appears on the screen.
I was able to see the screen turn on once and when I plugged in my USB OS it showed a fully loaded apple logo and bar but it just stuck there so I shut it down.

I wasn't sure how to measure J9600 without disconnecting it so I just measured the probe points next to it.
SSD_BOOT_L - 1.78v
SSD_PWR_EN_L - 0v
STORAGE_EN - 3.32v
SSD_RESET_L - 3.32v
SSD_CLKREQ_L - 0.09v

 

[2informaticos]

You still have corroded traces or components.
Use quality flux and reflow the BGA chips from the affected area.

 

[ytesfay80]

Okay everything seems to be working fine now. I did the flux and reflow + I saw that C9206 was missing from the board so I put one on there and replaced C9221 since it didn't look good.

Thanks again.