Figure the sound, light, sometimes, can be caused by large swings its voltage, can also be used by the load failure, mainly due to line scan failure caused by the power supply voltage fluctuations. C9bservice manual download site
 C9bservice manual download site
(1) after startup check C909 switch power supply output voltage, have significant motion, more than 120 v, have a cry and fell to a low, grating disappear. C9bservice manual download site
(2) left external 10 v power supply when the power is on C909 for load, fault elimination. Fault in the power supply circuit. C9bservice manual download site
(3) check the switch power supply, found the power switch transformer between the sampled data and the line flyback transformer winding (1) the foot. Careful examination revealed line flyback transformer circuit board cracks 1 foot, poor contact. The spot welding, fault elimination. C9bservice manual download site
After the printing plate fracture, sampling winding of the D907 C907 charging voltage is reduced, the equivalent of the output voltage is reduced, the IC901 adjustment function, make the switch tube conduction time lengthen, higher output voltage. Because the flyback transformer winding open circuit, the power supply work is lower than the line frequency, sound is produced. After connecting a breakpoint C907, D907 suddenly on sampling switch transformer windings in parallel, and the short time of switch power supply stopped, the output voltage is reduced, resulting in the grating when sometimes no.C9bservice manual download site