new build, no display, no POST, no beeps

Remove the graphics card, and try booting again with the onboard video device.  If that works, then you may have to disable the onboard before installing the new graphics card.

I ran into this same issue on an intel mobo.

Hi,

I've already tried that and same result.

Check that you haven't inadvertently shorted the reset pin permanently to earth by putting the connector onto the wrong pair of pins. If that connection is correct, pull or disconnect everything from the motherboard except the CPU, heat sink and fan, and the PSU, and see if you get any beeps. You should at least get the beep code for bad RAM. If the assembly is still silent, take everything out of the case again and check for short circuits under the board, perhaps from a bad bit of finishing or a metal mounting post in the wrong place. Also check the USB ports for foreign objects such as stray staples (yes, it does happen), and that the CPU is correctly seated in its socket.

If these suggestions don't resolve the problem then I'd suspect a DOA board, as that's rather more likely than a dead CPU.

Agree - CPU is unlikely.  It's a good board but the lack of beeps with no RAM is concerning.  It does sound like the board is bad.

Just checking to only other obvious issue - have you got both the ATX power connectors in place?
(Sockets ATXPWR1 & ATX12V1) and does the PSU support the correct voltages for those sockets (i.e. you're not using adapter cables to get the PSU to fit).

You might also want to try shorting the CMOS (link pins 2&3 of the three pins at CLRCMOS1

So only the PSU,  Power switch connector, CPU and heatsink are connected to the mobo and still getting nothing, no beeps.

Both ATX powers are connected. The large connector and the 8 pin one. Have tried clearing CMOS already using the jumper but same result.

Will take the mobo out later to check under the board

Ok no beeps, did you connect the speaker to to correct port, hence no sound. The board may be booting up fine
two your video card is bad. Hence no pictures.

all else e fail start over.

test if the board displays when booted OUTSIDE the case - eg on a table (non conductive)
that will show where the problem is : in the case/mounting or the new board
it can be a DOA case..

Also just to confirm you have the video card in pcie2 slot correct? This is the 2.0 slot.
 
If you have it in the top slot pcie1 this only supports 3.0 cards.

Your card is 2.0 only so you have to use pcie2 slot.

and verify the Aux CPU power connector is connected as well!

Just tried a replacement mobo (same model) and same thing (booting outside the case as well)

This is happening WITHOUT the graphics card, just using onboard display connection.

AUX CPU power connector is connected. Fans don't spin without it.

Your sure your connecting the power, power led switch,usb connection correctly.

Make sure there seated correctly.

Make sure clear cmos jumper is set to off.

i would also try WITH thevideo card - with power connected
but it looks definitely like a DOA
try removing the AC power + bios battery for a minute - then retry

Is it possible to get a picture with all the connections set up?

Is the 5v standby current rating on the PSU sufficient for the new board and CPU? If the latter demand more than the former can supply then the system won't start...

Despite all the people on here, i still think this is a CPU problem..
I have had the issue described here in the past, on an AMD Athlon from years ago.. Same issue..
If you pull the CPU, check for burning on the CPU, also make sure you didn't ground out the CPU on the heat sink..

it can be your cpu is too new for the bios, and you need to upgrade it first to V P1.90
see the list of supported cpu's :  http://www.asrock.com/mb/AMD/FM2A78M%20Pro4+/?cat=CPU

or it is simply not supported (i did not find your cpu there)