* Check the Antenna signal strength, whether it gives readings as per requirement. * Check the Diplexer stage * Check the Video Section properly for video signal generation. Which includes, Mixer, Adder, Gating Pulses, Sync Signal Generator etc. * Check the Sound Signal section. Which includes, Microphone, Modulator, Amplifier circuit. * If the reading are not match with the standard readings, there could have an problem in component. * Replace/ repair the component and check the signal again.