Abstract: Faults frequently occur to the light-emitting board of Valve-Based Electronic(VBE) system, so the paper, through cracking the circuit of the light-emitting board, analyzes and tests the optical coupler input circuit, logical control, first and second level drive circuits of laser tubes, and then locates vulnerable components that contribute to light-emitting board faults. It also builds a heat flow equivalent circuit simulation model to study the effects of ambient temperature on faulty elements to further find out reasons for component failures. Moreover,the paper puts forward improvement measures of VBE screen cabinets, light emitting diodes and field effect transistors of vulnerable components to avoid aging acceleration and failures caused by long-term operation of components under high temperature environment.

    Key words: valve-based electronic; light-emitting board; field effect transistor