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Hello,
please help me diagnose before i disassemble!
Not Working:
1 - (upon connecting mDP, MacBook Screen blinks, but ultimately doesn't detect the ACD)
Working:
I heard about re-soildering the LED-strip, but I'm afraid it's panel or LogicBoard. Please advice!
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@sony2k check to see if the voltage on test point TP81 on the logic board and chassis ground is between 23.3 - 25.7 V DC. That will verify that you get power to the backlight. If you do have power then it is your panel (LED array) if you do not have power then you have issues with your logic board.
This just to reiterate what Apple suggest:"
Quick Check
Blank / No Video, No Backlight
• No video
• No backlight
• Dim backlight
1. Verify display being used with supported system.
2. Verify USB/display/power connectors are fully seated.
3. Use with known-good system. If used as second display, check display preferences to see if display is recognized by system.
4. Check brightness setting.
Deep Dive
Check Result Action Code
1. Verify display’s USB hub and built-in camera are listed in the System Profiler’s USB device tree.
Yes Power supply and USB communication OK.
Go to step 3.
No Go to step 2.
2. Unplug and replug the Mini DisplayPort connector into a known-good, supported,
powered-up portable system and monitor the portable’s display. Verify that the portable’s display briefly turns off then back on.
Yes Display detected by system.
Go to step 3.
No Go to Dead Unit/No Power symptom code flow.
3. Darken room and connect to a known-good supported system. Verify backlight by looking for faint glow from display.
Yes Video signal from host system OK. Backlight ON.
Go to step 5.
No Go to step 4.
4. Verify that the LCD function interface cable and LED driver cable connections are secure. See Functional Overview.
Yes If connections are OK and secure and the display is still blank, go to step 5.
No If cable is damaged, replace all-in-one cable or replace function cable.
5. Shine bright (low heat) flashlight into the front of the LCD. Verify if an image is being displayed.
Yes Image present but backlight is not ON.
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Hey,
I did some measurements and:
TP81: 0.0 VDC
TP12: 0.0 VDC
Rest of Test Points are nominal, or within range.
Then I suppose it's the Logic Board? Or... something more?
If TP 12 has no VDC in then TP81 will not either. According to your measurements your board does not get any power.
Is it more likely that it’s LB or could it be PSU?
Check the power supply. Right now it definitely looks like you are not getting any power to the backlight.
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I opened the unit and additionally:
- fan not running
- PSU ‘whistling’
I’ll add comments when I disassemble the unit sometime later.
Krzysztof Starzecki 의