Picture 1. iMac cpu removal should not be this way, see some of the fragile pin bended. The right way is remove the memory bracket like Picture 2.

Picture 2. iMac A1419 cpu positioning dont look for the first pin but look at the shape that match the hole where i make a circle in green.

iMac A1419 which cannot be turn on (can be many other possible hardware issue) or suddenly turn off by itself (can be power supply issue as well) may be able to solve by replacing the spoilt cpu. In this case You can actually try to replace it Yourself buying desktop cpu available anywhere, after removing the logicboard from casing please remove the memory bracket like Picture 2. to prevent the pin to bend. This is also how You upgrade Your iMac A1419 i5 to i7 make sure the cpu series is the same or else the bridge chipset cannot recognise the cpu.

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