In general, very small, the sound of the computer in normal working hours, the sound of the cooling fan in addition to the sound of the hard disk read and write data, especially in switching Dell Inspiron 1545 adapter fan the sound. After long-term use of some switching power supply, while at work will produce some noise, mainly caused by poor power supply fan rotation. There are many reasons causing Dell Alienware M15x adapter fan rotation poor noisy
According to the data shows that failure caused by power accounts for about 20% of the total number of failures of the various parts of computer machine to 30%. Fault detection and maintenance on the part of the host, also must be established on the basis of the normal power supply. Let’s do some discussion the common faults of power. PC power supplyis generally susceptible to failure are the following: blown fuse in the power supply without input or output voltage instability, power output but no show boot, power load capacity. A description of each of its repair methods:

1. Blown fuse Failure Analysis and Troubleshooting

When such a failure occurs, the first to open the case of the Dell Alienware M17x adapter, check the power fuse is blown, pursuant to which can initially determine whether the inverter circuit is faulty. If so, it is not outside caused by the following three conditions: a bridge rectifier diode in the input circuit breakdown; high voltage filter electrolytic capacitors C5, C6 breakdown ·; inverter power switch Ql, Q2 damage. The main reason is because the oscillation circuit of the DC filter and transform work in the high voltage (+ 300V), the large current state for a long period of time, especially due to larger changes in the AC voltage, the output load is heavy, prone to the blown fuse fault. DC filter circuit consists of four rectifier diodes, two 100kΩ current limiting resistor and two 330uF electrolytic capacitors composed about; transform oscillation circuit is mainly composed of the two models in the same heat sink high-power switching tubes.
AC fuse blows, shutdown, unplug the power cord, and carefully observe the appearance of the high-voltage components of the circuit board breakdown burnt or traces of electrolyte overflow. Without exception, with a multimeter to measure the value of the input of: less than 2OOkΩ, backend local short circuit, and then measure the resistance between the two high-power switch e, c pole; less than 100kΩ, then the switch The tube has been damaged, to measure the resistance of the four rectifier diodes are reverse resistance and two current limiting resistor, to determine whether the normal multimeter to measure the charge and discharge. In addition, replace the switch tube, if you can not find the same model and select substitutes should be noted that the collector – emitter reverse breakdown voltage Vceo collector maximum allowable Toshiba PA3715U-1ACA adapter dissipation Pcm of the collector – base reverse hit The parameters should wear voltage Vcbo of greater than or equal to the original parameters of the transistor. Another note: must not detect a component damage, replacement will boot directly, this is likely due to other high-voltage components are still failure, in turn replaced component damage. Must conduct a comprehensive inspection of all high-voltage components of the circuit measurement, in order to completely rule out a blown fuse.

2. No DC voltage output or voltage output instability

If the fuse is intact, the load, at all levels of the DC voltage output, the possible reasons: power, open circuit, short-circuit phenomenon; over-voltage, over-current protection circuit failure; oscillation circuit is not working; power overloading; frequency rectifier filter circuit rectifier diode breakdown; filtering capacitor leakage.
The processing method; resistance to ground with the the multimeter measurement system board 11 5V power greater than 0.8Ω, then the short circuit the system board. Computer configuration is minimized, i.e. the machine, leaving only the motherboard, Toshiba PA3468E-1AC3 adapter, a buzzer, and measuring the output DC voltage, and if still no output, indicating a fault in the microcomputer power supply in the control circuit instead. Control circuitry integrated switching Toshiba PA3290E-2ACA adapter controller (TL-496, GS3424, etc.) and over-voltage protection circuit is normal is directly related to whether the output DC voltage control circuit work. Overvoltage protection circuit is mainly composed of small power transistor or SCR and related components, available multimeter to measure the transistor is the breakdown (if SCR need to weld under measurement), the resistance and capacitance for damage.

3. Power output, but no show boot

The possible reasons for this failure is “POWER GOOD” input Reset signal delay time is not enough, or no output “POWER GOOD”. Boot with a voltage meter to measure the output of “POWER GOOD” end (the computer attached to the Toshiba PA3714U-1ACA adapter plug 1 foot) +5 V output, and then check the delay components; +5 V output if so, replace the delay of the delay circuit when the capacitor can be.

4. Power load capacity

Power in to the motherboard, floppy drive power can work properly when connected to the hard drive, CD-ROM drive, or plug in the memory, the screen goes from not working properly. Its possible causes: transistor operating point is not selected, high-voltage filter capacitor leakage or damage, regulator diode fever leakage, rectifier diodes damage.
Exchange oscillation loop each of the transistors, to increase the gain, or adjust the working point of the transistor. Detected with a multimeter parts, replacement SCR, zener diodes, high voltage filter capacitor or rectifier diode can be.