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[SOLVED]820-3332 No backlight. Has video.

bjf

bjf

Member
Known-good 2012 test screen. Has flashing folder. No backlight. Spill damage, but very minimal and nothing near LCD connector or U9701. Any idea what I'm missing?

- BKLT_EN_L - 0V
- BKLT_EN_DIV - 4.3V
- F9700 is fine and has 12.6V on both sides
- PPBUS_SW_BKLT - 12.6V
- BKLT_EN - 3.15V
- 5V_S0 present
- D9701 Pin 1: 12.59V
- D9701 Pin 2: 12.29V
- Pin 1 of LCD connector has 12.29V
- R9753 and R9757 are both good and have continuity to U9701
- BKL_SW - 1.1V
- BKL_FB - 5.8V
- replaced U9701
 
bjf

bjf

Member
yes, 3.4V on SMC_LID.
.879 diode mode on both sides of D9701.
.530 on pin 10 BKL_SCL
.533 on pin 11 BKL_SDA

it's a weird one. everything seems in order. is LVDS_IG_BKL_ON significant?
 
D

dukefawks

Administrator
I asked if D9701 was shorted. Having the same diode reading on both sides can very well mean D9701 is shorted.

LVDS_IG_BKL_ON is for backlight on Intel GFX, boot happens on Nvidia.
 
bjf

bjf

Member
Got it, was thinking short to ground. Not shorted but I replaced it anyway because it shouldn't be the same value on both sides. It's 1.1 to ground in diode now on pin 2 and .890 on pin 1. And still not shorted. No change with new D9701.
 
bjf

bjf

Member
Of course I did..... :/

.......well, I'll admit, I don't think PRAM reset when I see no backlight. I will from now on, at least when I see one like this with no obvious hardware issues.

thanks for your help, working normally.
 
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