In the circuit analysis shows that the fax machine after boot, under normal circumstances should be showing on the LCD screen LCD "SYSTEMINITIAL" initialization (system), the six LLD light should shine at the same time, after a few seconds automatically extinguished. LCD and LED all by 5 v voltage power supply, LED, LCD has no display after boot, 5 v voltage is not added to the operation panel. At this time should first check the main control board and power board connector between P1 is loose, fall off, connect the cable with and without break the phenomena, such as the then P1 (3) feet of voltage is measured with a multimeter if there are 5 v. If there are 5 v voltage, then check the connector P10 (5) between foot and ground voltage (that is, the input voltage of 5 v operation panel), such as normal, you should check the connector P1O the connection between the cable with and without broken wires to the operation panel. If no 5 v voltage applied to the main control board, it should check the connector P1 to the connection between the power supply cable with and without break. zSqservice manual download site
 zSqservice manual download site
 zSqservice manual download site
Must be connected to the load when the electricity (electricity, so as not to damage the switch regulated power supply) inspection, found the main control board and power board, main control board and operation display panel between the connector and connect the cable no problem, the connector P1, P10 (5) to (3) the feet of no normal 5 v voltage between the main control board and operation display panel are not 5 v power supply voltage. This suggests that the fault in the power supply circuit. zSqservice manual download site
 zSqservice manual download site
Electricity measuring 5 v power supply circuit output voltage of 0 v. zSqservice manual download site
 zSqservice manual download site
Continue to measure CON1 voltage of 0 v, also the foot in ac input filter circuit or specify a converter circuits. zSqservice manual download site
 zSqservice manual download site
Remove power panel, check the ac fuses F1 in good condition, electricity measurement C25 ends for normal about 300 v dc voltage. At this point, can be connected to an oscilloscope to observe pulse transformer T1 for pulse voltage waveform in the secondary winding each, to determine whether oscillation circuit. Didn't start up after observation, converter, the converter circuit is the key element of damage, these key components may be Q1 and Q2, R6 and R7 and over-current detection resistance R2, etc. Static checking Q1 and Q2, R6, Q7, R2 and other components, find MOS field effect switch tube Q1 D - S open circuit, no damage for the rest of the components. Replace the Q1 energized after commissioning, various dc voltage return to normal, troubleshooting.

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