I have bought a car radio (AMPrime 4022D) that has ability to connect rear camera to it, so you can see the image on its screen. The problem is that radio doesn't detect the signal (blue screen). But on an old portable TV, video is shown normally. Camera, that I use, was bought separately.
I have tried to connect different resistors (later on trimmer) on signal line of coax cable, and figured out that around 700-800ohm the radio detects video signal but the image is black. Maybe there is slight presence of otherwise bright spots. Every time I wanted to reduce resistance, the screen became blue again - no signal. Then I tried to do the following: when image was black (signal present) I would shortcut resistor with a screw driver and the true image from the camera would momentarily appear on the screen! Then soon after image from camera appeared, the blue screen came back again...
I don't know exactly what is going on, but I connected oscilloscope on an open connector and measured voltages that appear 1V higher than on specification of composite video. Could that be the reason, the signal couldn't be detected. I have also tested this camera on another more "modern" car lcd screen and the symptoms are similar... no video detected, except momentarily when camera is powered on.
What is the cause that this is happening and what could be a solution?