Hi. I've read the above which has given me some hope - perhaps the combinations I've tried of various RAM insertions still need work to be done, but I fear my situation might be a bit different. Very grateful for any advice.
I've a Vintage early 2013 iMac 27" and until a few days ago the device has worked flawlessly since new. After an electrical storm which cut the power to the device it rebooted without problem. However, after 15 - 30 minutes of use there was an electrical noise and the screen went blank, device turned off. With the same power cord and alternative power cords the device would not resume, including a 15-20 second period without power. I've tried removing all the RAM and then leaving one bank in (TOP) and now joy - no power on no noise, no screen.