Hi everyone! I've bought a second-hand iMac that was described as having a RAM issue (three beeps). I took the RAM out and put it back on again and the computer boots (I can hear the chime). However, the screen doesn't (black, no light whatsoever). Since this iMac came without keyboard and mouse, I've used a standard wired keyboard to reset the SMC and PRAM, but that didn't work. I've connected the iMac via miniDP to my Dell monitor, and I can see the Yosemite background blurred. Thus, I thought: OK, perhaps the iMac is expanding the screen. However, the shortcut to mirror the display (CMD+F1) won't work. What am I missing? Edit 1: I've tried to run a Recovery Disk via USB stick, but the screen won't work. If i do this while connected to the Dell monitor, it shows a grey screen, and then a black illuminated screen (but nothing from the main monitor). The seller assures me that everything was OK with the computer when it started to beep (and I have no reason to believe he is lying) Edit 2: I've found a wired mouse, and the cursor shows in the external display, but right clicking does nothing.