Apparatus and method for judging the status of external device control circuit in composite TV

摘要

The present invention relates to an apparatus and method for determining a state of an external device control circuit in a composite TV that allows an operator to test whether a printed circuit board is normal for a plurality of AV devices. The composite image input from an external first AV device is provided. Among the signals, the multiplexer selectively outputs only the signal determined by the microprocessor, and the audio / video signal processor that processes and outputs only the signal determined by the external device selection port of the microprocessor among the signals input from the tuner or multiplexer, and the CRT driver An integrator for integrating a color difference signal to obtain a voltage value proportional to each color difference signal, an adder for summing voltage values corresponding to the color difference signals from the integrator, and an addition value of the color difference signal output from the adder is greater than a reference value; Comparators are also configured, but the operator When the printed circuit board of the device is connected to the two input terminals of the multiplexer and input options for selecting the first AV device and the second AV device in turn through the key input unit, the first AV device selected through the multiplexer and the audio / video signal processor The color difference signal of the second AV device is passed through the integrator, the adder, and the comparator in the CRT driver to check whether there is a normal signal, thereby displaying normal (OK) or abnormal (NG) for the AV device selected by the operator. I did it.