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820-00165 Missing BKL_PWM

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SairFecht

Member
I've got an 820-00165 here that came in with no backlight, working perfectly apart from that (image is fine).

Only visible corrosion I could see was a tiny amount around U5110 which I cleaned up, it seemed entirely cosmetic.

D7701 - 8.6v both sides
XW7720 - 8.6v and clean
BKL_EN - 2.83v
BKL_PWM - 0v

5 or 6 PRAM resets done. Two LCDs tested (original, plus known good).

Image is on and seems solid, can clearly see the MRI screen (which is what I stuck in the USB port to test with).

Sorry if I'm missing something obvious here (I feel I am), brain dead at the moment.
 
S

SairFecht

Member
Swapped DC-in, no difference. Actually... haven't tried adjusting under macOS, but assumed (perhaps foolishly) that the PRAM reset would auto-max the backlight. I'll boot into an OS and try that.
 
2informaticos

2informaticos

Administrator
Staff member
SMC_LID should be OK, as you get image.

Could be bad U7701, but try first forcing BKL_PWM.
Remove R7704 and tie together BKL_EN/PWM.
If still 8.6V at backlight output, then change U7701.

Also be sure all return resistors are good.
 
S

SairFecht

Member
SMC_LID is normal and working, return resistors all seem good too.

Joining EN and PWM still results in no backlight. I've ordered some replacement drivers, hopefully have them for Monday.

Thanks both!
 
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