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LEDs 1&2 lit, 3&4 out. It won’t recognize an external monitor so I can’t change any settings etc. Could it be the PGU or just the battery? How can I tell?
Fortunately the GPU replacement card on this machine is not high dollar. Here’s how to replace it: iMac Intel 21.5" EMC 2389 GPU Card Replacement I hace never seen one of these newer batteries go bad.
