Tape out of receiver for phono to amp?

My setup is Mag.3.6r, Krell 250,and KSP 7b preamp with a vinyl front end. After setting this up I found one channel not working and the sound seemed muted in the other. Suspecting the preamp I used a receivers tape out in place of the preamp. Know all I get is amp hum through both the speakers and amp as well.