gIn order to prevent damage to the motherboard or other parts, after the ATX power supply breaks down, it must be removed, examined and repaired. Generally, switching power supply can not work in light ship condition. Because the voltage output ends are in parallel with load resistors, after the ATX power supply is removed, its breakdown will not be expanded due to no load.
After power on, even if the power conversion part does not work, there should be +5V voltage output for the auxiliary power supply (APS). That is to say, the measuring interface 19 feet over the ground has +5V voltage. If there is no SB voltage output or the voltage is instable, check the AC-DC conversion and the auxiliary power supply circuit.
AC-DC converter section
Measure whether the D3 negative voltage is about 300V. If the fuse is burned, time delay fuse of the same model must be replaced and other wires or fuses can not be used as substitution optionally. Fuse being burned generally indicates a more serious breakdown, which should be treated with caution. Common reasons are damage of rectifier diode, breakdown diode damage or leakage of filter capacitor, damage of switch tube Q11, or serious short circuit of other parts over the ground.
The inspection center of auxiliary power supply is Q11. Under normal conditions, auxiliary power supply works in oscillatory condition, and Q11 base test by a multimeter is a negative voltage. Common phenomenon is that starting resistor R11, R12 open circuit causes no oscillation starting vibration to circuit. In addition to that, Q12, ZD1, ZD2, Q21, LM431, IC11 should be examined step by step. These 450 ATX power supply components are easier to be damaged than resistance, so resistance can be finally checked to see whether there is breakdown. The reason why SB voltage is instable or it deviates from the normal value is mainly the changing of value of resistance of R24, R25, which are two precision resistors.
In normal circumstances, after PS/ON feet connect with ground, power oscillating circuit can be started. If the voltage outputs are normal, generally it describes the power supply is working well, but whether the P.G. signal is normal should be paid attention to. P.G. signal is the signal of the output power to the motherboard, and indicates that power supply is working well. If the P.G. is abnormal, it will cause the main board output high level to the PS/ON and power oscillation part does not work.
Use an oscilloscope to check whether there is oscillation pulsed output of 5, 8, 11 feet of KA7500B. Another key point to check is the control fee 4 feet of KA7500B. When it is high level, there is no pulse output in the circuit. Various protection circuits of ATX power supply are very rigor, and any breakdown will cause abnormal 4 feet. During maintenance, pay attention to analysis of 4 feet high level caused by various reasons, and analysis of LM339 voltage pins, making sound judgment with reliable analysis.
en.goldenfield.com.cn is a leading computer case supplier , who has been dedicated to developing and producing computer peripherals - PC Case, Switching Power Supply, Multimedia Speakers, Mouse and Keyboard, etc since 1993.
After power on, even if the power conversion part does not work, there should be +5V voltage output for the auxiliary power supply (APS). That is to say, the measuring interface 19 feet over the ground has +5V voltage. If there is no SB voltage output or the voltage is instable, check the AC-DC conversion and the auxiliary power supply circuit.
AC-DC converter section
Measure whether the D3 negative voltage is about 300V. If the fuse is burned, time delay fuse of the same model must be replaced and other wires or fuses can not be used as substitution optionally. Fuse being burned generally indicates a more serious breakdown, which should be treated with caution. Common reasons are damage of rectifier diode, breakdown diode damage or leakage of filter capacitor, damage of switch tube Q11, or serious short circuit of other parts over the ground.
The inspection center of auxiliary power supply is Q11. Under normal conditions, auxiliary power supply works in oscillatory condition, and Q11 base test by a multimeter is a negative voltage. Common phenomenon is that starting resistor R11, R12 open circuit causes no oscillation starting vibration to circuit. In addition to that, Q12, ZD1, ZD2, Q21, LM431, IC11 should be examined step by step. These 450 ATX power supply components are easier to be damaged than resistance, so resistance can be finally checked to see whether there is breakdown. The reason why SB voltage is instable or it deviates from the normal value is mainly the changing of value of resistance of R24, R25, which are two precision resistors.
In normal circumstances, after PS/ON feet connect with ground, power oscillating circuit can be started. If the voltage outputs are normal, generally it describes the power supply is working well, but whether the P.G. signal is normal should be paid attention to. P.G. signal is the signal of the output power to the motherboard, and indicates that power supply is working well. If the P.G. is abnormal, it will cause the main board output high level to the PS/ON and power oscillation part does not work.
Use an oscilloscope to check whether there is oscillation pulsed output of 5, 8, 11 feet of KA7500B. Another key point to check is the control fee 4 feet of KA7500B. When it is high level, there is no pulse output in the circuit. Various protection circuits of ATX power supply are very rigor, and any breakdown will cause abnormal 4 feet. During maintenance, pay attention to analysis of 4 feet high level caused by various reasons, and analysis of LM339 voltage pins, making sound judgment with reliable analysis.
en.goldenfield.com.cn is a leading computer case supplier , who has been dedicated to developing and producing computer peripherals - PC Case, Switching Power Supply, Multimedia Speakers, Mouse and Keyboard, etc since 1993.