Because TDA7388 is a four-channel power amplifier integration block, its four channels are exactly the same, so as long as the R×1K file of the pointer multimeter is used to measure the resistance values of the four input terminals, four output terminals to the ground and to the power supply, if the integration block is normal, then its four groups of resistance values should not be much different, if one or two of the difference is too large, That means the block is broken.