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macrumors newbie
Original poster
Jun 11, 2021
Hi! After reading al the posts I have a problem that no one has experienced, I try to upgrade an imac 2019 27" i5 3,1Ghz to i9 Radeon Vega 48 Logic board but always got LED2+LED3 + Fan Spining, back to original Logic board, systems working. I have upgrade the original logic board to an 3,7Ghz i5, working perfectly, upgraded with Samsung 860 2TB SSD + NVMe SN750 2TB + 128GB(4x32GB Crucial Apple compatible modules).

I have tested 3 new logic boards,2 from original i9 Radeon Vega 48 and 1 from original i5 Radeon Vega 48, without CPU, I have tested two fresh CPU, i9 9900K & i9 9900KF, got the LED2+LED3 + fan spinning, tried all module position, withoout SSD, without NVMe, battery removed before CPU installing, no pins damaged, tried 2 diferent PSU (LiteON & Delta).

Months ago I do the same operation but the i9 Radeon Vega 48 comes with i9 9900K integrated, no issues, starts inmediatly with the same upgrades (128GB, 2TB SSD+2TB NVMe).

As this logic boards can handle this i9 processors, and there some reviews, can this model of logic board had a problem with CPU? Or can we have a problem with the LVD cable or similar? I need to return the logic boards to the dealer but It´s frustrating not have a solution... I have spent a lot of time and money with the CPU to find a solution, I leaved in an Apple Service center but they can only test with a fresh i9 Radeon Vega 48 logic board with CPU that comes from Apple and it works in my iMac 27" 2019, the are not going to test the CPU between boards as I did, anyone can help or is there any other tip to know what´s happening? SMC or EFI problem matching the CPU?

I see a lot of reviews of upgrades from standard logi boards non Radeon Vega and they can hold all i5 & i9 CPU from this 2019 specifications but someone has replaced an i9 9900K or i9 9900KF CPU with a Radeon Vega 48 Board?


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