hooked up TT and preamp to receiver sound fades out after 4-5 seconds

I just bought a realistic lab 400 turntable and hooked it up to my receiver a pioneer vsx 56txi into the phono input. I will add that I am a total newbie to this. I got nothing no sound at all. I researched and bought a phono preamp behringer PP400. I hooked it into the phono in on the audio of the receiver and connected the ground wire and had sound for about 4-5 seconds and than no sound. I tried connecting to the cd audio in and same thing only sound for about 4-5 seconds. Everything else works fine regarding sound. Stumped. I would appreciate any suggestions you might have.