LCD backlight Issu Z8A REV D

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • kalilinux25
    Badcaps Legend
    • Mar 2018
    • 2084
    • ZAMBOANGA SIBUGAY
    #1

    LCD backlight Issu Z8A REV D

    Hi good day i have a quit a bad issue of this board , I alrady change the scren but I can only ssee a dim light od display showing acer logo. Ive tsted the pins showing
    CN8
    Pin 40 19v
    Pin 36-34 has 3.3v
    Pin 32-33 has 3.3v
    Pin 30 has 0v

    Im very new with this issue and I dont want to add more damge to the board hope somoen can guide me..
    Attached Files
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14023
      • Canada
      #2
      Re: LCD backlight Issu Z8A REV D

      Hi. Is the replacement display a 100% new display or at least confirmed to be a working unit with a working backlight?

      The computer works fine with an external HDMI monitor?

        Comment

        • kalilinux25
          Badcaps Legend
          • Mar 2018
          • 2084
          • ZAMBOANGA SIBUGAY
          #3
          Re: LCD backlight Issu Z8A REV D

          Originally posted by mon2
          Hi. Is the replacement display a 100% new display or at least confirmed to be a working unit with a working backlight?

          The computer works fine with an external HDMI monitor?
          Yes the Lcd is new and it works in hdmi out

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14023
              • Canada
              #4
              Re: LCD backlight Issu Z8A REV D

              According to CN8 schematic, pin 30 should not be zero volts. Please see attached.

              Can you trace back this pin 30 and confirm if there is a stuffed resistor @ R6 or R9?

              Only one resistor should be present on the logic board.

              Respectively, when this resistor is found, check the OTHER side of the resistor to confirm if there is a voltage rail present @ +3V (R6) or +5V (R9).

              Also, investigate the hall effect IC (lid sensor?) as per the attached schematic. Is this working correctly?

              What is the voltage on BLON_CON?

              Perhaps the host CPU believes the LID is closed so it is dimming the display accordingly to save on power.
              Attached Files
              Last edited by mon2; 04-07-2021, 10:56 AM.

                Comment

                • kalilinux25
                  Badcaps Legend
                  • Mar 2018
                  • 2084
                  • ZAMBOANGA SIBUGAY
                  #5
                  Re: LCD backlight Issu Z8A REV D

                  Originally posted by mon2
                  According to CN8 schematic, pin 30 should not be zero volts. Please see attached.

                  Can you trace back this pin 30 and confirm if there is a stuffed resistor @ R6 or R9?

                  Only one resistor should be present on the logic board.

                  Respectively, when this resistor is found, check the OTHER side of the resistor to confirm if there is a voltage rail present @ +3V (R6) or +5V (R9).

                  Also, investigate the hall effect IC (lid sensor?) as per the attached schematic. Is this working correctly?

                  What is the voltage on BLON_CON?

                  Perhaps the host CPU believes the LID is closed so it is dimming the display accordingly to save on power.
                  The =3v and 5v is preent into the end of the two resistor
                  The r9 and r6 are no stuff
                  check the BLON_CON 3.3V

                    Comment

                    • mcplslg123
                      Badcaps Legend
                      • Jun 2015
                      • 7262
                      • india
                      #6
                      Re: LCD backlight Issu Z8A REV D

                      What about the LID switch as suggested by @mon2??

                        Comment

                        • kalilinux25
                          Badcaps Legend
                          • Mar 2018
                          • 2084
                          • ZAMBOANGA SIBUGAY
                          #7
                          Re: LCD backlight Issu Z8A REV D

                          Originally posted by mcplslg123
                          What about the LID switch as suggested by @mon2??
                          when I tried to check the pins of q38 im not getting any voltage on all pins

                            Comment

                            Previous template Next

                            Related Topics

                            Collapse
                            • triplefour
                              UN65TU700DF picture and sound but no backlight. BL tests ok but repl. PSU didnt fix!
                              by triplefour
                              this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
                              i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
                              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...
                              09-13-2023, 10:43 PM
                            • DanPoka
                              Guide me through repairing a Dell p2210f LCD ccfl backlight monitor
                              by DanPoka
                              I bought this p2210f dell monitor to fix. Schematic is the same as p2210.
                              Behaviour is that monitors comes on but then backlight switches off almost instantly. If I look with flashlight I can still find the "No signal message". So definitely a backlight issue. Trying to advance the issue I proved that the protection circuit is switching off the backlight by shorting out C3 and resistor to disable the INL chip then re enable by removing the short.
                              This is where it gets interesting. When I disassembled the monitor to solder leads on c3 capacitor I noticed the backlight flickered...
                              02-15-2025, 05:05 AM
                            • Comp_Pro
                              No Backlight Macbook A1990 820-01041
                              by Comp_Pro
                              Hello all,

                              Am trying to figure out this backlight issue with this A1990 Macbook Pro.

                              Tests performed:

                              There is no backlight even with a good screen.
                              Backlight IC is receiving the correct support voltages.
                              Fuse F8400 ok
                              Current sense resistor R8400 ok
                              Backlight IC is receiving 3.3V on enable pin.
                              Backlight IC receiving voltage from PPBUS_G3H, aprox 12.5V.
                              Backlight IC receiving 5V from PP5V_G3S
                              Backlight IC BKLT_SCL and BKLT_SDA both measure 0.545V diode mode to ground
                              I2C_BKLT_SCL and I2C_BKLT_SDA both measure...
                              05-06-2024, 10:23 PM
                            • cheebster
                              iPad Pro 12.9 5th Gen Backlight Issue
                              by cheebster
                              Hello, got an iPad Pro A2378 12.9 5th gen with no backlight. Got another test unit without screen, tested the screen, still no backlight with the test unit.
                              Figured out the backlight on the screen was bad, ordred a new backlight from mobilesentrix, *carefully replaced it* without damaging the lcd, oh well.
                              Final result, issue is still there, the screen has no back lights. So i'm back to square one, with 3 hours less and 100$ out, issue still on the screen.
                              The panel is still ok, i can see the apple in the middle of the screen when it kicks in, just no backlight.
                              Anyone...
                              05-20-2025, 09:17 AM
                            • canadaboy25
                              LG Flatron 24EN33TA No Backlight When Cold
                              by canadaboy25
                              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...
                              03-07-2023, 12:23 AM
                            • Loading...
                            • No more items.
                            Working...