820-4924-A no video

[javier_herart]

The Macbook came in for no video issue.

I was able to get external video.

I got 0V on backlight and screen voltage.

When took out the board and connected to start measuring one the ICs on the Jack got burned, no sure why. I am testing with another jack now...

Now I am not able to test the get external video nor on the screen.

-PLT_RESET_L: 3V
-Caps Lock: Responds ok on USB keyboard
-Takes 600mA

Ive heard some of these board work only when battery connected?????


Any idea? Thanks

 

[javier_herart]

Forgot to mention:

No liquid damage, just some dust and crap un some areas on the SMC side. (does not look like corrosion)

 

[2informaticos]

Which chip got burnt?
Are you testing with 2015 LCD assembly for sure?

Check in the first seconds (when chimes), for voltage at pins 28-30 of J8300.
If appears, pin 9 and DP_INT_HPD must go high at same time.

 

[javier_herart]

See attached the burnt chip on the jack.

When chimes :
PP5VR3V3_SW_LCD: 5.2V (after a moment: 0V)
LCD_HPD_CONN: 3.3V (after a moment: 0V)

 

[2informaticos]

That is a TVS diode; clean these pads.
Do you still get orange light now?

BTW, I asked about DP_INT_HPD too; that is the signal received by PCH.

 

[javier_herart]

Sorry

DP_INT_HPD: 3.3V (after a moment: 0V)

Yes, I do get green/orange light with the burned jack and of couser with the good one to.

 

[2informaticos]

Then PCH should recognize LCD and maintain the voltage.
If not, it may not like the LCD used; be sure to be 2015 model!
Test with known good one.

 

[javier_herart]

Yes, I was testing with its screen.

Tested with a know good and I have video.

Still wondering why I couldnt get external video ?

 

[2informaticos]

Force it, disconnecting internal LCD.
If still the same, test with another RIO board and cables.

 

[javier_herart]

Just wanted to mark this one as solved.

Replaced the display and the machine is wotking fine.

About the HDMI, it seems that my external monitor decided to die. External video is working.