broken rca's?

ok well i have a viper d1200.1, it was going strong for a while but not anymore. the rca inputs started going out a while ago and i just had to jiggle them to work. now they dont work at all. i brought it in to a repair shop here and had them resolder the rcas. got it back and nothin... the only way the amp will play is if i plug one rca plug into the slave input, and if i do that i cant work the amp controls unless i run another (it's very quiet like this).

what do i have to do? i opened it up, the rcas are soldered good, dunno what next.