Could be anything with the information you have. First I would look towards the PSU since we have no red power light. This also could be due to physical trauma such as fall damage, water, electrical. Bad connections is also a possibility if attempts to repair were done in the past. If this box was opened in the past do a check of the cables. Last system I had a no power issue on, it was caused by the cable not being connected to the board for power/eject.
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