After the machine is power on and off the relay and action can be heard, comprehensive protection circuit which can eliminate the accused of this factor. By the standby indicator lights glow red glow GuanHeng to infer, failure is the main switch power oscillation circuit caused by vibration. Maintenance of the D7 switched on test (1), (2) feet between dc voltage is 290 v, normal, rectifying mode switch control circuit element is good. And detection of thick film blocks IC801 start voltage of 13.2 V, 5 feet of oscillation starting circuit work normally. Measured again IC801 (4) feet voltage of 2.6 V (figure values for 1.2 V), the voltage is too high to make feet IC801 internal control over-current protection circuit. Causes of IC801 4 feet high voltage are: IC801 diamond effect switch tube leakage current is too large; IC801 (2) the foot of the external flow detection is proposed.theoretical larger; T801 secondary rectifier filter circuit leakage or load short circuit; Rectifier filter output overvoltage protection monitoring electrical components caused by bad protection Q803 saturated conductivity or Q803 beam junction leakage damage etc. Try to narrow the fault range, desoldering D822 pins, remove the control function of voltage on 4 feet again short boot detection + B and output voltage of 140 v, is normal, the machine has been observed at this time, all the control function back to normal. Judge fault were certainly caused by R816, R817, D820, Q803 overvoltage protection monitoring circuit composed of bad cause misoperation caused by. Q803 was detected at this time of b, c, e voltage of 4.1 V, 13.1 V, 3.6 V, and the rectifier output voltage of 290 V when the tube to normal b and e voltage should be 0.3 V and 0.2 V respectively. Conclude that Q803 is in on state, and doubt R816 ~ R818 value or 10 v voltage regulator tube D820 damage. Measured again D820 cathode on the voltage of 9.4 V, obviously lower than that of D820 zener conduction threshold voltage 10 V, suggesting that D820 conduction is its poor performance or leakage caused by damage. Trial domestic 1 w / 10 v voltage regulator tube substitution D820, boot attempt to restore the original circuit, the machine work back to normal, troubleshooting.

 2    1 2 Next Last