Few days ago I bought a used PC and used monitor. I tested the monitor with my old PC (I use it to type this post) and it works, but the PC I bought only showed black screen when turned on. The motherboard is "ASUS P8H61-M LX R2.0REV. 1.02". I noticed some things:
When I first tested it, it only shows black screen, so I checked the VGA card and left fan (near HDMI slot) not spinning. I tried to lift the right area a little bit and the left fan worked once but then it stopped again and I never able to reproduce this. I also bought HDMI to VGA converter and connect both motherboard's VGA slot and dedicated GPU's HDMI slot, each with separate monitor. No result, both just gives black screen;
The CPU casing has shocks when connected. I checked the PSU fan and it is spinning when the PC turned on. The motherboard LED also lit when it connected to a power source;
This PC has 2 RAM slots, and I checked each of them by removing one of them and re-install one for each slot. No beeps. I once did not fully inserted RAM into its slot, as I'm new to repairing PC and I didn't know how to insert RAM stick properly, and the CPU beeps;
There is clanking noise and sometimes "whoosh" noise, either from DVD (empty) or HDD (pre-installed 2 HDDs). I did unplug all SATA connectors, 2 SATA connectors leading to HDD, and 1 SATA connector leading to DVD. Its still clanking. The topmost HDD is WD Caviar Blue, and I haven't check the bottom (second) HDD yet;
I did remove CMOS battery, waited for 1 hour, and no result. It's still black screen when turned on.
With all said, I stopped diagnose the problem by myself, as I might do damage to the PC I just bought. I never get into BIOS or booting up into OS so far, so I may think this not a simple problem that can be self-repaired by myself. I did clean all dust from VGA card, RAM, and motherboard, and its still only give me a black screen when turned on.