Late 2013 21.5” iMac: I upgraded RAM and HDD to SSD all from iFixIt. Upon reassembly, LED #1 is solid and LED #2 blinks every 5 sec or so. No startup chime, and fan only “twiches” when the LED #2 blinks. How can I determine if I need to replace the PSU or if it’s a motherboard replacement I’m facing? Also - seems odd that the computer worked fine until I swapped out the memory. Any help much appreciated!