Internal Display Black External Workings Fine But Imac Intel 21 5 Emc 2308

Chosen Solution

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iMac working on external display problemInbuilt display not working .There are only 3led physically present on motherboard No.4 which is mentioned in attached image start with iMac start but turn off automatically after few seconds.(after removal of lcd screen)

but still external display working fine.Very very light display appear sometimes. confused inverter problem?lcd to inverter cable problem?backlight problem?.

You need to replace the LED driver board. iMac Intel 21.5" EMC 2308 LED Driver Board Replacement