Troubleshooting
A power supply unit is vital component of a system that supplies power to various components of the system. The power supply unit is an electronic component and may show some problem due to which the system may not start. Due to faulty power supply, the components of the system may also get damaged. As a result, troubleshooting the power supply problem is also an essential task for maintaining the system. You can use various tools for troubleshooting SMPS. Various tools include a low power fine tip soldering iron and fine rosin core solder, Digital Multimeter (DMM), Twiser, Brush, Screw Driver set and Desoldering Pump are used to diagnose the problem in SMPS.
System Does Not Start:
When you switch on the system it does not start due to a fault power supply unit. The power supply may start but may not be able to supply the appropriate voltage needed by various components of the system.
To troubleshoot this problem:
Make sure that the power connector of the system is properly plugged-in the main power supply junction.
1. Check the internal connection of the system after removing the system case cover.
2. Check the connection of the motherboard connector of the power supply unit with the motherboard.
3. Check for any occurrence of the short circuit which might have happened inside the system case.
4. Check if there is some problem with the main power supply junction.
Power Supply Fan does not Work or Emits a Lot of Sound
The power supply fan is not working when the system is switched on or makes a lot of noise.
The problem occurs if the power supply fan is not functional or if lots of dust is accumulated in the fan motor.
To troubleshoot this problem:
1. Shutdown the system, remove the system case cover and clean the dirt or dust from the fan and power supply unit with a vacuum cleaner or with hand blower.
2. Check the power supply fan and replace if it is defective
UPS not Handling Power Problems
The UPS is not handling the power supply problems very well and does not function when there is a blackout. The system may also automatically shut down at times.
To troubleshoot this problem:
1. Check the capacity of UPS battery for supporting the electronic current load for the system.
2. Change the battery of the UPS if needed by reducing some load from the UPS.
3. Check the voltage selector switch, placed at the back of the system case and ensure that the voltage selected is according to the region.
4. Check the connections of the motherboard and the disk drives with the power supply unit.
5. Remove any extra disk drives if not needed during the current operation.
Before Opening SMPS
1. Check the AC line.
2. Check the power cord and line voltage selector switch whether it has been set to 230V AC.
3. Remove all daughter cards, FDD, HDD and supply connector and check the PG signal.
4. Short pin no 13 and 14 to see the fan is rotating and then check the O/P voltage by DMM.
5. If the SMPS does not work when connected to motherboard then check whether there is a problem with SMPS.
After Opening SMPS
1. Open the SMPS and check the filter capacitor voltage and discharge the capacitor.
2. Examine the PCB properly and understand the circuit diagram.
3. Check for loose contacts, blown fuses, burst out filter capacitor and switching and power start transistor.
4. Check for bad soldering at the point of transformation, resistor and power transistors.
5. If the points are not soldered properly then solder them again and then check the output.
6. Start diagnosis by referring to manual.
7. Check the output voltage between pin 12 and GND of IC 494, If it shows 20VDS then power start selection, double transformation with diodes at secondary winding are OK, if it's not then there is a possibility in the input coming or with the IC.