Analysis and maintenance: Most of the reasons why all the buttons on the remote control do not work are caused by the damage of the crystal oscillator. If it has been dropped or there is no "beep" sound at all with the radio check, you can directly replace the crystal oscillator with a new one. After replacing the new crystal oscillator, if the fault cannot be eliminated, you should first measure the voltage across the crystal oscillator. When any key is pressed, there will be obvious voltage changes at both ends of the crystal oscillator, which indicates that the oscillator can generate pulse signals. The second is to check whether there is a relatively weak voltage change at the output end of the remote control signal of the integrated block. If there is a change, check whether the driving triode and the infrared emission tube are damaged, otherwise most of the integrated blocks are defective.