Just another guide for you, I’ve just done this {28 JUNE 2019}
solutions for 3 Beeps
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1. Upgraded your RAM[br]
2. RAM undetected
If any of your RAM goes undetected, also the chime doesnt happen and the only sound is of 3 concorrunt beeps then:
1. Press and hold the power button so the fan goes off.
2. Loosen the 4 screws mounting the RAM holder slot '''a bit'''.
3. insert small folded paper or old credit card cutting as plastic swag/cuff
4. Power your Mac. [If this works, Hurray!! Close off the lid and get back to work] If this doesnt
5. Tight the 4 screws, arm your Mac. This should make it work, i suppose.
6. If it does work, thank me @bakedsamosa and iFixit for simplifying the replacement.
7. Close the Lid already. Get back to Steve Job’s best creation.