Here, I am going to share some of my experience with you that is Trouble Shooting tips and tricks. So, Have a look and start to solve your problems. Trouble shooting means making a PC works well after certain problems and troubles. It makes easy to know the problems and solve. Remember that you are going to work with a machine. So, if it is possible get some basic tools like following before starting it.
- Documentation of the product.
- Container for placing a screw and other small components.
- Screw driver
- Operating system CD’s and good boot disk. 
- Proper antistatic wrist strap.
- Utilities software.
Problem:
I) No display on the screen ( Display Problem)
Cause:
- Loose connection of the monitor cable with display care.
- Display card not fixed properly in the display.
- Position of monitor’s controller is changed or monitor is defective.
- Processor not fixed/ installed properly.
- Memory is not fixed properly.
- Due to the defective display card.
- Power supply may be defective.
- Due to the reverse connection of HDD cable.
- System board is defective.
Solution:
- Connect the monitor cable with display card.
- Fix display card in the slot properly and check the display card is damage.
- Check the monitor control buttons like contrast, brightness etc,
- Check the memory sticks if they are installed properly.
- Change the display card if damage.
- Measure the output voltage of SMPS. If not available change it.
- Check the system board.
- Check the HDD cable and correct it.
II) PC is dead ( No active at all)
Cause:
- Due to the AC main supply.
- Due to the defective on/off switch.
- Due to defective system board.
- Due to defective SMPS.
- Due to wrong connection of power cable on the system board.
Solution:
- Check the source of main AC
- Check the on/off switch and its connections.
- Check the output voltage of SMPS. If not available replace it.
- If it is ATX systems check the system board.
- Check the p8 and p9 connector on the system board, if it is at power supply.