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Diagnostic LED No 4 is OFF while computer is ON. No display, Nothing Checked with flash light, showing nothing 3.5v showing on pin 3 of the connector so I checked the LCD panel with another iMac found that the display is working fine. what should I check / do next? Thanks in advance
The inverter board would affect the backlight. But you stated the flashlight test failed so thats not your issue here. Which model do you have the EMC 2133 or EMC 2210? The EMC 2133 offers a MXM GPU board unlike the EMC 2210 which does not. You either need a new GPU board or a new logic board. As your GPU has failed. Thats assuming the system was not damaged in opening it. A common issue in this series is damaging the LVDS cable or the logic board connector.
