Analysis of maintenance

Symptom: hands into the hot air outlet without blowing hot air.
Analysis of maintenance: check the fan and heater normal, measuring no SCR gate trigger voltage control transistor Ⅵ measure of c pole rectangular wave signal output, auto hand dryer suspected adverse e optocouplers, measured with a multimeter Rxl0 block ③ Optocouplers , ④ feet between the positive and negative resistance are infinite, the forward resistance should be several jet hand dryers, reverse resistance is infinite, it is determined that the internal photodiodes open, resulting in lack of SCR gate trigger voltage It can not be turned on. After replacing optocouplers, troubleshooting.