The machine "3 without" the cause of the problem may be: (1) the microprocessor IC1101 did not work properly, {30} feet can't boot output low level signals. (2) the switch power supply itself fault, no + B110V and around + 9 v voltage output. (3) the line scan circuit, especially line output circuit over-voltage over-current fault occurs, the protection circuit trigger conduction, switching power supply to stop working. (4) protection circuit misoperation can be Q902 itself. LwEservice manual download site
First used segmentation method and dummy load method, measuring the switching power supply output voltage is normal. Break operation of flyback transformer T761 {10} feet and printed circuit board connection, between the positive and ground C909 connected to 60 w bulb, measuring output + B110V end of 0 v. Examination revealed CP901 (HM9207) damage and R905A burn out. Renewals, switching power supply + B110V and + 9 v output is normal. Remove the dummy load and boot recovery circuit, is still "3 without". Protection circuit for measuring Q902 control no more than 0.5 V voltage, no over-voltage over-current protection. LwEservice manual download site
 LwEservice manual download site
 LwEservice manual download site
Microprocessor IC1101 (sp) M34300N4-555 work must have three conditions, measuring IC1101 {42} feet only 4.3 V power supply side; Reset all landowners feet only 4.2 V. {and} and {} 35 feet X1101 (4 MHZ) and its Q1102, ZD1102, DZ1101, C1101, C1103 peripheral components such as no short circuit failure; Measuring IC1101 {30} feet power on/off control end for high level all the time. Why IC1101 {42}, all landowners, {30} feet voltage are not normal? Whether IC1101 internal short-circuit damage? LwEservice manual download site
To test the Q904 emitter voltage of 7.5 V, IC501 24} {foot voltage of 7.4 V (normal should be 12 V), D700 the anode voltage of 0 V (normal) should be 12.5 V. For microprocessors IC1101 power supply side {42} 7 feet and reset the feet of voltage, also after R913 and step-down dual power supply, so the D700 the anode voltage of 0 v explain only a set of power supply, switching power supply and output stage T761 output (3) feet another set of power supply to 0 v, causing IC1101 {42}, all landowners, {30} feet voltage are not normal; At the same time also suggests that line output stage did not work at all. Check Q791 sd882 (2) has been damaged, renewals, or "3 without".

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