When the machine is working properly, the measured screen to the motherboard socket CN203 each terminal voltage: DATA terminal is 4.6V and stable, CLK end of 4.64V, CS terminal is 4.83V. When a fault measured DATA terminal voltage is 4.2 ~ 5.0V and volatile, indicating that the OSD IC CPU to communicate with the motherboard unsuccessful, CPU due ROM data loss or disorder and can not send the correct data, the OSD IC and therefore does not work .