In order to review the failure rate of PC monitor under normal environmental conditions, we experimented for various levels of each factors, e.g. Power on/off, DPM mode, using voltage incoming Surge, Torque strength etc. According to the results of experiment and SN ratios we investigated that the causes of the failure for the horizontal output TR of monitor are Mode change, dispersion of Torque and $h_{FE}$ and these are critical effect. For the new reliability test we suggested that strengthened part tests in IQC branch, Torque change controls in the TR specification are necessary.