(5) +5 V normal repair process does not boot without +12 V, +24 V voltage.

 

Fault coverage is relatively large, there is on / off circuit , the main power oscillator circuit , the main power sampling feedback circuit. Maintenance should be the first test CON3 connector ( 7 ) whether there is power voltage of 5V pin , if not then the fault in the motherboard standby circuits , such as the figure below normal maintenance steps can be inspected .

 

Of particular note is that the power board from the R21, R22, R31, R51, R52, U8, R33, V4, R13 etc. mains detection circuit , open or more elements such as poor +15 V will cause the on / off voltage can not be successfully applied Ul (NCP1377B) main power chip ( 6 ) feet , the main power supply fails to start . +12 V and +24 V and no output. If you suspect there is a fault in this circuit can be V4 (9012) ce very short , such as power starts normally , indicating a fault in the circuit , such as still no power on , indicating a fault in other circuits.

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