On the operation panel are both LCD and LED by the + 5 v power supply voltage, the circuit as shown. sg5service manual download site
 sg5service manual download site
Boot after the LCD and LED are not normal, and measure the + 5 v power supply voltage of 0 v respectively check: when the power is R23, R27, R18, R32, Q1 and Q2, Q3 and Q4, Q11 components and devices without exception. The judge not to + 5 v voltage operation panel. sg5service manual download site
 sg5service manual download site
First check the power supply circuit for + 5 v voltage output. Remove the power supply parts, after electrify the multimeter measuring dc voltage power supply of 10 core on the PCB connectors CON1 (3) feet (+ 5 v) to ground voltage of 0 v. sg5service manual download site
 sg5service manual download site
 sg5service manual download site
Due to the 12 v, + 24 v and + 5 v voltage generated by the switch oscillation circuit. In order to determine the fault location, and then measure the + 12 v (CON1 (5 feet) and - 12 v (1) feet of CPN1) voltage. Measure the 12 v voltage is normal, explain the power converter circuit and the input circuit of the circuit are normal, fault in the + 5 v voltage output circuit. Measuring voltage stabilizer (U2) input voltage is normal, and the output voltage of 0 v, the judge U2 has been damaged. Change after U2 (7805), a fax machine work is normal, troubleshooting.sg5service manual download site