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820-00165 no backlight
- Thread starter No-Clean
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BKL_PWM controls U7701, not viceversa!
Post BKL_EN level too.
We need more info to help.
Post voltage and diode mode to ground on both pins of D7701.
Be aware of XW7720; pictures can be found on the forum.
Do you get image at least (on internal LCD)?
External video OK?
Post BKL_EN level too.
We need more info to help.
Post voltage and diode mode to ground on both pins of D7701.
Be aware of XW7720; pictures can be found on the forum.
Do you get image at least (on internal LCD)?
External video OK?
No-Clean
Member
BKL_EN 2.8v
D7701 8.59v both legs
D7701 586 on the left and 408 on the right
XW7720 looks almost gone, a little better than this one https://drive.google.com/file/d/18UR9ufMnaWRTbwZwNjTTxmIcHGCNpSBl/view but damaged, so I ran a jumper from what was left of that pad to D7701 and also checked continuity from there to pin 5 of U7701, but still nothing
Yes I see the folder question mark when I light the LCD from the back, did not check external video, but I assume is fine.
D7701 8.59v both legs
D7701 586 on the left and 408 on the right
XW7720 looks almost gone, a little better than this one https://drive.google.com/file/d/18UR9ufMnaWRTbwZwNjTTxmIcHGCNpSBl/view but damaged, so I ran a jumper from what was left of that pad to D7701 and also checked continuity from there to pin 5 of U7701, but still nothing
Yes I see the folder question mark when I light the LCD from the back, did not check external video, but I assume is fine.
If you've changed U7701, post now diode mode (red probe at ground) on all return resistors.
Do PRAM reset few times.
If BKL_PWM still low, then remove R7704 and run a wire from R7715 to C7704.
Check if backlight comes on.
Do PRAM reset few times.
If BKL_PWM still low, then remove R7704 and run a wire from R7715 to C7704.
Check if backlight comes on.
No-Clean
Member
JohnB8812 C7797 indeed is 8.56v
2informaticos all return resistors measure 0.630
R7704 is 0.504v
I ran a wire from R7715 to C7704 after removing R7704 and no backlight either, folder with question mark flashes when I use a flash-light but no backlight yet.
2informaticos all return resistors measure 0.630
R7704 is 0.504v
I ran a wire from R7715 to C7704 after removing R7704 and no backlight either, folder with question mark flashes when I use a flash-light but no backlight yet.
Did you try known good compatible LCD assembly?
No-Clean
Member
Yes, good know compatible LCD.
I put a new LP8550 and all is working again, thanks 2informaticos and JohnB8812 for all the help.
I put a new LP8550 and all is working again, thanks 2informaticos and JohnB8812 for all the help.