820-01521 no back light

Seems simple...... but..

U8400 LCDBKLT_EN_L is missing.
U8400 has power and BKLT_EN_R is present.

I replaced U8400 from a donor but wanted to check in before I tried another one.
What am I missing?


Staff member
"LCDBKLT_EN_L is missing"
If you mean is 0V, I would say is very present (active low).
Remember the end "L"...

Post D8410 voltages and diode mode to ground.
Did you try known good working LCD assembly?
no. IT won't pull the 12v down
the pull down signal is missing
PPVOUT_S0 Backlight is of course zero

L8400 PP5V_G3S is present.
(Diode test) 0.3 forward 1.0 backward "little odd" compared to test boards "I do not have a known working one"

I did swap Q8401 as well

Tried my LCD test board.

>>>>>> update <<<<<<
I found it. It was a cap. I checked resistance on that buck caps and some how missed that it was 60 ohms.
It is amazing at how fast L8400 shuts it down.
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