Regulated power supply common fault solution
1. The regulated power supply has output but does not self-test when it is switched on.
This is mainly due to the power supply PW-OK signal delay time is not enough or no output. After switching on the power supply, use a voltmeter to measure the output of PW-OK (8 pins of the power plug) with or without +5 V. At this time, you should check whether the comparator LM393 is damaged. If the delay is not enough, you should check the resistor R104 and capacitor C60 in the delay circuit.
2. Regulated power supply output voltage is not allowed
If only a voltage deviation from the rated value, while the other files are normal, the voltage of the integrated voltage regulator circuit or rectifier diode damage. If all deviate from the rated value, it is by IC1 1, 2 feet error amplifier, R39, C32 error amplifier negative feedback loop, sampling resistor R33, R34, R35, constitute +5V, +12V automatic voltage regulator control circuit has a fault.
In the replacement of regulated power supply circuit in the secondary tube should be noted, because the inverter operating frequency is high, generally greater than 20kHz, in addition to the load current is also larger, so the power supply in the +5V gear Schottky high-frequency rectifier diode SBD, the rest of the gears are also used to restore the characteristics of the high-frequency rectifier diode FRD. so when replacing the rectifier diode to find the same type as far as possible to avoid re-damage.
3. Fan does not rotate or rattle
Computer regulated power supply fan is usually connected to the +12V DC output DC fan. If the power supply input and output everything is normal, and the fan does not turn, mostly for the fan motor damage. If the sound, one of the reasons is due to the long-term operation of the machine or transport process of intense vibration caused by the fan of the four fixed screws loose; the second is too much dust inside the fan or oil bearing oil, as long as the timely clean-up or add the appropriate amount of lubricant, the fault can be eliminated.
4. Controlled start DC power supply no output
(1) T2 original side VT3, VT4 push tube damage, R54 resistor resistance value becomes large; (2) half of the DC power supply after controlled start.
(2) half-bridge power conversion circuit switching tube VT1, VT2 at least one open circuit.
(3) anti-bias capacitor C8 capacity becomes small or open circuit.
5. Poor load capacity of the regulated power supply
Poor load capacity of the regulated power supply is mainly manifested as: power supply in light load conditions, such as only to the system board, floppy drive power supply, can work normally, and in the match with a large hard drive, expanding other equipment, often power supply work is not normal. This is generally the power conversion circuit of the switching tube VT1, VT2 performance is not good, filter capacitors C5, C6 capacity is insufficient. Replacement of filter capacitors should pay attention to the capacity of the two capacitors and the withstand voltage value must be the same.
