[例1]故障现象 一台昆仑S471型47cm彩电在雷雨天收看节目时,突然一声响雷致使市电中断,机器也随之出现三无故障。 分析与检修 开盖后目视检查整机无明显烧毁元件。瞬时开机测开关电源主电源+130V输出仅28V,且伴随有“吱吱”叫声,说明开关电源能起振工作。输出电压过低可能与负载过重有关,经查果然行管(2SD1426)击穿。为防止因电源故障引起行管再次击穿,暂不接行管,在+130V对地接上330Ω/50W电阻做假负载,瞬时开机,电压高达190V,可见行管正是由此原因而损坏。 本机开关电源的稳压调整采用的是厚膜块A301(JU0114),试调+B调整电阻W321无效,关机后在路 [Example 1] Fault phenomenon A Kunlun S471 47cm color TV to watch the program during a thunderstorm, a sudden thunder and lightning caused the mains interruption, the machine also appeared three no problems. Analysis and Inspection After opening the lid visual inspection of the whole no obvious burning components. Instantaneous power-on test switch power supply main power + 130V output is only 28V, and accompanied by “creak” sounds, indicating the switching power supply can start work. Output voltage is too low and may be related to the load, the check really ran under control (2SD1426) breakdown. In order to prevent the power failure caused by the line pipe breakdown, temporarily not in charge of the pipe, connected to the ground in the +330 V 330Ω / 50W resistor to make a false load, instant power on, the voltage up to 190V, we can see that the line is damaged by this reason . The local switching power supply regulation is thick film block A301 (JU0114), trial adjustment + B adjustment resistor W321 is invalid, after the shutdown in the road