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Versión actual por: Michael ,

Texto:

+'''EDIT Nov. 9 2020: see updates at bottom of post'''
+
+'''ORIGINAL POST:'''
+
To add to the info found on this problem:
The current fix seems to basically override the overcurrent protection on the monitor. As the backlight strips age, they require more and more current to start up, and eventually the monitor refuses to supply this current, and the backlight stops turning on. One fix is to override this protection, which is not great in the long run and also causes the backlight to be only on full brightness.
To truly fix this issue, one should purchase new backlight strips on ebay or aliexpress. This will cost $10-20. Then, take the panel out of the monitor, and disassemble the panel frame. The LCD panel is attached to the back on the metal frame by ribbon cables. Open it like a book, remove the films and diffusers, and you will have the backlight strips accessible. Replace the backlight strips, rebuild the monitor, and things will work like new. It’s a PIA, but in the end, you will have a working monitor with fresh backlight strips that should last somewhat indefinitely and you will retain brightness control and overcurrent protection.
I have accomplished this repair successfully on an ACD. I have also replaced the backlight strips on a 2011 27” iMac, which is the exact same procedure as the ACD as the panel (LM270WQ1) is shared between them.
+
+'''EDIT Nov. 9 2020''':
+
+Replacing the LED strips did not permanently fix this issue. I think it helped some but frequently the display backlight would flicker before failing to turn on at all. At this point, I replaced the logic board with a known good board. I’ve had no problems since. Unfortunately, I don’t know what exactly went wrong on the logic board.
+
+My theory on why this happens:
+
+# The backlight overcurrent protection kicks in at too low a current
+# The aging LED strips require more current to start up
+Thus, if your monitor is suffering from (1), then fixing (2) by replacing the LED strips will reduce the ''severity'' of the monitor’s symptoms. This will be a ''temporary'' and ''incomplete'' fix because (a) the strips will age and (b) the overcurrent protection kicks in too soon anyway. Instead, replacing the motherboard will be a more robust fix, because the aging LEDs shouldn’t really have much of an impact (27” iMacs use the same panel and I’ve never heard of them having this particular failure) and because it will hopefully be a logic board with properly functioning overcurrent protection.
+
+
+
+'''UPDATED TL;DR:''' Replace the logic board.

Estatus:

open

Aporte original por: Michael ,

Texto:

To add to the info found on this problem:

The current fix seems to basically override the overcurrent protection on the monitor. As the backlight strips age, they require more and more current to start up, and eventually the monitor refuses to supply this current, and the backlight stops turning on. One fix is to override this protection, which is not great in the long run and also causes the backlight to be only on full brightness.

To truly fix this issue, one should purchase new backlight strips on ebay or aliexpress. This will cost $10-20. Then, take the panel out of the monitor, and disassemble the panel frame. The LCD panel is attached to the back on the metal frame by ribbon cables. Open it like a book, remove the films and diffusers, and you will have the backlight strips accessible. Replace the backlight strips, rebuild the monitor, and things will work like new. It’s a PIA, but in the end, you will have a working monitor with fresh backlight strips that should last somewhat indefinitely and you will retain brightness control and overcurrent protection.

I have accomplished this repair successfully on an ACD. I have also replaced the backlight strips on a 2011 27” iMac, which is the exact same procedure as the ACD as the panel (LM270WQ1) is shared between them.

Estatus:

open