test with a minimum connected : mobo, 1 ram stick, cpu, video card, 1 HDD, 1 DVD
Here my troubleshooting procedure :
Precautions :
-During connecting or disconnecting devices, be sure to have the AC removed
-Temporarily ground yourself, or use a wrist strap for ESD prevention
-With a new motherboard : verify if all mounting standoffs correspond with the holes in the mobo !!
Or test the motherboard outside the case, on a wooden (non conductive) surface
-Clean the system from dust, then test with the minimum setup - disconnect also all peripherals and network cables :
-What to connect : only motherboard + CPU + 1 ram stick, video card, power supply
-Verify that the 4-, 6- or 8-pin CPU Aux power plug is connected
-Verify that the VIDEO card has a power connecter - if yes, connect the power to it !
Now power on your PC : on boot, do you have a display?
-if NO it is one of the connected: RAM, Power supply , video card or monitor, so if possible swap ram, Power supply, video card or monitor - leaving only motherboard and cpu
-if YES, connect devices till the problem shows
*** note : if the fans are running, this shows there is 12 V present from the Power Supply; this does not mean the PS is ok, you still need 3.3 V and +5 V as well; and other signals.
Additional tests and things to try :
-boot without ram, it should beep; (also, without video card)
-try bios default settings, (if possible) or clear the bios by removing AC and bios battery
-renew the CPU heatpaste, and verify that the heatsink is mounted flat on the CPU, allowing for a good thermal contact
-you can also check the motherboard for bad capacitors as shown here :
http://en.wikipedia.org/wiki/Capacitor_plagueThe term POST refers to the Power On Self Test procedure - here a link with a short explanation
http://www.pchell.com/hardware/beepcodes.shtml