A Vizio TV has a power board that converts AC electricity from a wall socket into different DC voltages that power the screen and the main circuit board, which in turn provides power to the audio and control circuits. A bad power supply could cause a number of problems, including having sound but no picture.
Complete Power Supply Failure
A transformer at the input to the power supply of a Vizio TV reduces the voltage to a lower level, and rectifier circuits change the AC to DC. The TV works with an input voltage level from 90 to 240 volts AC, at either 50 or 60 Hz. The regulators in the power supply must keep all voltages constant regardless of the input variations. If any of these components fail, the power supply will not work at all and there will be no sound or picture.
Partial Failure
The power supply in a Vizio TV has an inverter and other components that develop the voltage to send to the viewing screen. If any of the components in this section fail, the screen will not illuminate. If the components of the power supply that provide voltage to the main circuit board work, the sound should also work. There are two other circuit boards that could fail and cause the Vizio to have sound but no picture: the connector board and the video board.
Connector Board Failure
The connector board in a Vizio TV accepts signals from the input jacks and forwards them on to the main board for processing. Although there are few components on the board, a failed or loose connection to the main board could prevent video signals from entering. More common problems that cause sound but no picture are a loose or defective connecting cable and having the TV's selector set to an input that has no video signal.
Video Board Failure
A Vizio TV also contains a video board that accepts signals from the connector board via the main board. It processes the video signals and sends them back to the main board and then on to the display. The video board performs no audio functions, and if it fails, there is sound but no picture. Note that unless you are a qualified technician, do not attempt to open a Vizio TV to repair it. You could void your warranty or cause further damage.
Tags: main board, power supply, connector board, signals from, sound picture, video board