820-3476 no image / missing 5V LCD enable

[Fizzl92]

This 820-3476 turns on and seems to work noemally. Board and also the rest of the machine look like new. CPU is getting hot, fan is spinning but no image (on internal LCD and external screen too) I checked:
sys_pwrok = 3.4V,
the light on an external mouse is blinkin,
S0_LCDBKL = 0V.
noticed no voltage on l8300 and followrd this to U8330. I measured Pin 1,2,5,6 and they are all 0V (coming from the CPU) and they all are not shorted. Pin 8 = 3,34V, Pin 3,7 = 0V. Now i am stuck.

 

[2informaticos]

"the light on an external mouse is blinkin"
USB mouse should get steady light.
Else, don't search for image/backlight...
Test in both USB ports.

 

[Fizzl92]

Thank you for the answer. I mean that the light is blinkin when the mouse is upside down. So its searching a surface. If i move my finger close to the sensor it stays on... Its hard to see the light on my test moust if ist on the table the right way...Sorry for that.

 

[2informaticos]

L8300 should get voltage few seconds at least, when the board starts.
You can check it without LCD even.
If LCD is OK, LCD_HPD_CONN should reach 2.5V; then L8300 will remain at 3V.
If LCD_HPD_CONN stays low, L8300 voltage disappears too.

 

[Fizzl92]

Than the problem should be U8340. 3V3_S0 is there at C8340, R8340 is <100K OHM, no shorts at Pins 1 & 4 but only 0.2V at Pin 4 and 0V at Pin 1...

 

[2informaticos]

"Than the problem should be U8340"
Why?
LCD_HPD_CONN comes from display.
PP5VR3V3_SW_LCD should appear first.
So at least one of LCD_PSR_EN, or EDP_PANEL_PWR should appear in the first seconds...

 

[Fizzl92]

I noticed that i cant do a PRAM reset. I connected the speakers (both) but cant get it to chime. But cpu is getting warm and fan is spinning... PPVCC_S0_CPU = 1.76V. I am really confuesed by this one. So maybe there cant be an image right now? Both enables (LCD_PSR_EN, EDP_PANEL_PWR) are low all the time.