820-3115 no video

MDY

New member
820-3115 board. Liquid damage I repaired 1 month ago and now back here again. Problem was arroun lvds connector. I replaced it again but no video, no backlight. I miss PP3V3_LCDVDD_SW
I checked U9000 and no short there. I also miss LCD_IG_PWR_EN

Mouse is on
 

dukefawks

Administrator
LCD not recognized. Try a known good LCD assembly and check pins 4 6 and 7 of LCD connector. Also check that SMC_LID is high.
 

MDY

New member
Sorry if I dont understand you, but screen to be recognized I should have at least one uncondition present power supplay to the screen. Isnot that LCDVDD?
 

dukefawks

Administrator
pin 4 supplies 3V to the EEPROM in the LCD that has the EDID information for the system to "see" the LCD. So pins 4 6 7 should always have 3V.
 

MDY

New member
You are always right. L9008 - 80 ohm
Will replace tomorrow and test. This is the problem I think.
 

MDY

New member
I replaced this coil and now backlight is ok and video too. Everything work now.

But when I removed the lvds connector before I damage pins LED_RETURN_1 and LED_RETURN_6
However backlight is ok. There are no conction betwen LED_RETURN_1, LED_RETURN_6 and LP8550

It is easy to connect them as there are resistores but I am suprised it works. It make sense? LED_RETURN are not important??
 

MDY

New member
Backlight is off again. When I power the board screen blink in white and then became black again. 20 seg later blink again and sometumes backlight appear for 3-6 seg only. After 40seg I noted thet LP got hot. Any thing suspect? I already replaced LP8550
 

dukefawks

Administrator
Yes the return lines check all 6 of them for shorts to GND, shorts between then and continuity to the LCD connector.
 
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