Troubleshooting Beep code

[IsaacO]

Hi there, ive been having issues with my PC, I think Ive finally diagnosed the issue but have no idea how to fix it.
A couple of days ago my motherboard broke, I think the bios was corrupted, and it got stuck in a boot loop. I wasnt too worried however, as I had a working spare motherboard lying around. Once I had set it all up, I powered my sytem on only to discover it would give me a beep code and not display anything.
After going through the ususal troubleshooting steps (checking connections, reseating RAM and GPU etc.) I still wasn’t able to trigger any sort of display on my monitor. I managed eventually to find a meaning for my beep code online, (one long beep, two short) which was that I was experiencing a video error and nothing could be displayed, which tallys with the issues I am experiencing.
I am now at my wits end, and have no idea how to fix my issue, any and all suggestions will be appreciated, thanks in advance.
Specs:
AMD athlon 860k
AMD radeon 290x 8GB (sapphire vaporX)
MSI A78M-E35 V2
4Gb crucial 1300mhz RAM
8Gb Adata 1600mhz RAM
600w cooler master psu
Wd blue 1tb HDD

 

[Zerk2012]

pull out 1 stick of the miss matched memory, reset CMOS and try again.