820-3023A Missing PP3V3_SW_LCD_UF

[Kittu]

Hi:


I will appreciate any help in diagnosing missing PP3V3_SW_LCD_UF from U9000 due to which the system is unable to detect embedded LCD panel.
On checking I find that LCD_IG_PWR_EN (input to U9000) is also low.

System boots and external display port is working.

Please Guide...

 

[2informaticos]

PP3V3_SW_LCD must appears in the first few seconds, usually when board chimes.
Then DP_INT_HPD should go high.
If not, PCH doesn't detect LCD and disables 3V3_SW_LCD.
If OK, then voltage is maintained.

Did you try known good compatible LCD assembly?

 

[Kittu]

Tried with known good panel and rechecked the connection pins. No 3V3_SW_LCD still...

 

[2informaticos]

Put voltmeter on that line, start the board and wait.
That voltage MUST appear even without LCD connected; but will disappear rapidly I suppose, in such case.
Check if at least U9000 enable trys to appear...

 

[Kittu]

Hi!
Yes, the supply does come after 5 seconds for a couple and then disappears.

On investigating further I found the case of a bad pad under L9004 leading to the system not registering the EDP. Replacing the Inductor and making good the connection restored the EDP display as well as backlight.

Thanks again for your help !