The machine without grating and audio fault can be made of switch power supply, line scan circuit and protection circuit and so on, and the line scan circuit is ok and protection circuit, switching power supply will be issued a "creak" sound, so no grating, no sound, no sound fault, is caused by the switch power supply. The power failure don't burn out the fuse F901 show again no short circuit flow phenomenon. 2X2service manual download site
(1) open the back cover, check the 2 a fuse, not broken, electricity measurement Q901 collector voltage of 280 v, normal should be between 260 ~ 280 v, rectifier filter circuit works well. 2X2service manual download site
(2) shutdown check Q901, R907, R908, R910, R911 components, such as open circuit found 0901 launch, the replacement of new 2 sc1942 after work. 2X2service manual download site
(3) if measured Q901 collector voltage of 0 v, a common fault components are R7901 D901, and insurance tube poor contact, switch transformer T901 primary open, pin empty welding, circuit board copper platinum breaking, etc.2X2service manual download site