I extracted this circuit from a satelital tv decoder to get the modulation part, the up coaxial is the input and the other is the output. It have a lot of pins and a pin that says "5v". I will test the 5v power in this pin and the metal case and touching the pins with a video signal. If anyone can, please help me.

Thanks! 

You would need to command it from some microcontroller (likely via i2c), for the modulator to do anything at all...
You need to study the datasheets of the ICs used there...