If the ______ section in a TV has failed, the result is "No Sound, No Picture".

The correct answer is Horizontal Output Transistor.

Concept:

The horizontal output transistor (HOT) is a crucial component of a television's circuitry. It serves multiple essential functions in generating a picture and sound.

In a cathode-ray tube (CRT) television, the horizontal output transistor is a part of the horizontal deflection circuit that helps move the electron beam from left to right across the screen. The horizontal deflection circuit provides a sawtooth waveform signal generated by the flyback transformer, to produce a magnetic field that sweeps the electron beam horizontally across the screen. This is repeated line by line from the top to the bottom, leading to a complete production of a picture.

On the other hand, the high voltage required for the operation of the CRT, such as the anode voltage, comes from the flyback transformer which is driven by the horizontal output transistor. If the HOT fails, the flyback transformer isn't driven adequately, and the high voltage required to operate the CRT isn't produced. This leads to both sound and picture failure -- as the deflection system doesn't work, and there won't be any high voltage for the CRT.

Let's briefly look at the other options:

2) Vertical Output: This refers to the vertical deflection system of the TV. If it fails, problems will occur in the vertical dimension of the image, such as a horizontal line appearing on the screen or no vertical deflection, but this would not cause both sound and picture to fail.

3) Sync Separator: The function of the sync separator is to extract the sync pulse information from the composite video signal. If this component fails, the result could be loss of synchrony between the transmitter and receiver, causing a rolling or jittery picture, but this wouldn't make the sound disappear.

4) IF Output: This is the Intermediate Frequency output stage. It's part of the receiver's circuitry where the signal is demodulated to retrieve audio and video information. Although a failure here could affect both sound and picture, it's not typically referred to in the context of "no sound, no picture", as some sort of noise or static is often still present.