I need help regarding a Panasonic DVX-100B camcorder.

Basically, what I'm trying to do is record audio directly from a phono preamp into the camera.
However, the camera needs a video signal as well, or else it doesn't record audio or video at all. I tested this at school with a DVD player.
The camera has two audio inputs and one video input - all RCA jacks.
I have it set up so that the video is coming from the "video out" jack of a VCR, and the audio is coming from the preamp.
However, nothing is showing up on the camera, even when the preamp is not part of the signal.
This camera has a VCR mode and a recording mode, and as the name implies, the VCR mode can be used to capture from VHS onto MiniDV.

Can someone PLEASE explain if I am doing something wrong? I have been trying to get this camera and preamp working together for this entire week, and they will NOT cooperate.

Thanks in advance.

The technique I'm using for a VCR DOES work with a DVD player. This is probably significant.

The problem has been resolved. The culprit? A faulty cable.