iMac not starting after upgrading CPU and pci-e storage
I attempted to upgrade my 2019 5k 27” imac by changing the CPU and the pci-e storage, and replacing the sata disk with more storage. I bought components and tools from OWC and a new i9 9900K CPU.
I followed the official OWC guide for getting into the imac, which seemed to work quite well, but when I put the components back together and before reattaching the screen I tried to start the imac to be satisfied everything was in order.
I pressed the power button. The fan starts, but there is no POST (or bong noise) and the display is just black.
I’ve looked at the LED diagnostic lights
and it looks to my knowledge that LED 2,3 are lit when I power up the imac, LED 2 is lit when the AC is connected. But not LED 1 at any point, or 4 or 5 when the display is connected.
Does anyone know what to try at this point? I have tried reseating the CPU but get the same result. The other things I will try are:
- reseat the RAM (haven’t changed this component thought, and worked fine before)
- put the old components back
Any other suggestions gratefully received before I sent for repair before inevitably deciding it is too expensive to repair economically.
Hi Dan, I don't think so though I've had to add and remove the screen to test it
I'll have a read through your link, thanks again.
To answer this question - the solution which worked for the initial question was to reseat the RAM. The five LEDs then lit up as expected and the computer worked as upgraded.
I damaged the display power cable completing the reassembly of the iMac - the LED shows the Apple logo on startup but there is no backlight. I can’t determine whether the logic board has been damaged (probably given that the 5th LED is permanently lit as per @danj’s comment), or whether the cable is fried, and I need a new screen. I’m not sure it is worth paying to find out at this point when I have an external monitor which works for sure.
I hope this helps future ifixiters.
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Hi! I got same problem, I have 3 diferent logic boards with Radeon Vega 48, all the same issue, led2+led3 and fan spinning. Ram, using default 4GB+4GB not starting, tested with 4x32GB Crucial compatible and same. If I do this with the default logic board, it works with the same iMac 2019 27". Did you use Command+Alt+P+R to reset the RAM?
Hi. @mepstein6 Can you share the processor i9-9900K model that you used in the upgrade, is it SGR19 or SRELS?
SGR19 for i9 9900K and SRG1A for i9 9900KF, did you
Mean that should work on SRELS version? Is the one that come with the special
Hexagon box, the SGR19 comes with standard box, can be the solution of my problem?
success, i upgraded to i9-9900K, but one disaster (hope not), after power up, the display has a hairline pinkish fine line. i checked again the eDP and it seems they are connected very well, but still there's this line. dang.
@biohazard32 i9-9900K SRG19 is OK as an upgrade CPU
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