Liquid crystal display device

A liquid crystal display device comprising:

• a liquid crystal panel;
• a controller configured to control the liquid crystal panel;
• and
• a relay substrate provided between the liquid crystal panel and the controller, wherein:
• the relay substrate and the controller are connected by a plurality of cables;
• the relay substrate comprises a plurality of first connectors to which one end of the cables is connected;
• the controller comprises:
• a microcomputer;
• and
• a plurality of second connectors which are paired with the first connectors and to which the other end of each of the cables is connected;
• the relay substrate and the controller comprise a line pattern to form a test circuit which feeds a test signal back to an input pin of the microcomputer from an output pin of the microcomputer, and which transfers the test signal from the controller to the relay substrate and returns the test signal from the relay substrate to the controller in each pair of the first connectors and the second connectors;
• and
• the microcomputer is configured to output the test signal from the output pin, and to determine a connecting state of the cables that connect the relay substrate and the controller based on a state of feedback of the test signal to the input pin.