Hi to all, I have a Mid-2010 iMac (21.5inch, 3.06GHz Core i3) with 16GB of RAM (recently upgraded, 2 x Hypertec 8GB kit (4GBx2) - HYS31325684GBOE) and a 1TB Crucial MX300 SSD drive (also recently upgraded), running OS X El Capitan. Since the purchase there were no issues with the iMac. However, after the memory upgrade, I got the three successive tones, then a five-second pause, repeating (RAM doesn't pass a data integrity check) a few times. This happened after either a forced shut down, or after a kernel panic once. Whenever that happened, I had to unplug the iMac, remove the memory access door, remove the memory and put it back in place. This was the only way to stop the startup tones. Of course, this made me suspect that the memory may be faulty. I run the AHT with no issues. Today, after a few updates, I had to restart the iMac to complete the updates. While restarting, when the iMac was about to boot again, I got the three successive tones again. So essentially, not only the iMac did not boot, but also the updates were not completed successfully. I tried removing and re-installing the memory, but now the iMac does not boot into Mac OS. I can hear the fans starting, but I get no boot sounds and nothing on the screen (no apple logo, no nothing). I tried: 1. Unplugging for 30 seconds and trying again 2. Holding down the Option key when booting No luck. Does anyone have a clue on how I can troubleshoot this? Thank you.