Re: Need help 820-00923 no backlight Newbie here
Fixed it, the problem was faulty Q8400
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Re: Need help 820-00923 no backlight Newbie here
Did you check for shorted on the backlight power rail?Leave a comment:
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Need help 820-00923 no backlight Newbie here
Hello there, newbie here
Have a MacBook pro to repair with no backlight. Thought that it was a faulty screen, so tested with good known working screen but still no backlight. There are no liquid signs at all on the board, the board looks clean as new.
So started tracing all power rails and spot that PPVIN_S0SW_LCDBKLT was missing after Q8400 so found and replaced faulty capacitor C8473 and that fixed this rail but still have no backlight.
Started investigating further and spot that U8400 LCDBKLT_FET_DRV is 0V and it can't open Q8401. So is it a U8400 faulty or the issue could be somewhere else ?
These are the readings from U8400:
LCDBKLT_SW - 0.12V
GND_BKLT_SGND - 0V
LCDBKLT_FET_DRV - 0V
PP5V_S0_BKLT_D - 5.13V
ISNS_LCDBKLT_N - 13.03V
ISNS_LCDBKLT_P - 13.03V
BKLT_SD - 9.32V
BKLT_PWM_KEYB - 0v
BKLT_SCL - 4.61V
BKLT_SDA - 4.52V
BKLT_EN_R - 3.34V
PP5V_S0_BKLT_A - 5.13V
BKLT_SENSE_OUT - 0V
LCDBKLT_FB - 11.19V
GND_BKLT_SGND - 0V
Any suggestions would be more than welcome.
P.S. The MacBook starts and works perfectly just no backlight, I can see Apple logo and so on.
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unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even... -
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Hi all,
I've got an LG Flatron 24EN33TA with a backlight issue. The problem began with the monitor not powering up after sitting for a long time (overnight or during the day throughout work). When I would wake the computer up, the backlight would flick on for a second then go out. Sometimes it would take many tries to get it to come on. Once the monitor came on, it worked flawlessly until another long duration of being powered off.
I thought the problem would be bad caps but I checked both of the caps on the board and they are fine. I also tried powering the monitor from... -
TCL 75S421
PSU BOARD: 40-L402H8-PWD1CG
it shows not even a flash of backlight when powering up.
but the tv appeas to turn on and i can hear the sound of the menus moving and clicking. i can power down the tv with the button.
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with mb connected, PSON...
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