signal works on motherboard

Specs: MOBO - GA-78LMT-S2P AMD-FX 6100 2x4GB DDR3 RAM HD Radeon 7770 & GTX 950 OC PSU - AYWUN Mega Power Elite 750 I get no signal to monitor when plugged into my gpu, but when connected to mother board I get signal, I thought my Radeon HD 7770 card had died so I bought a - Gigabite WINDFORCE...