These can include overheating, periodic boot-up failures or errors, parity errors, lots of noise, and even electrical shock when the case or connections are touched. If your power supply is showing any of these signs, it probably needs to be replaced. Never attempt to repair one yourself. Always take it to a technician. Or just buy a new one.
Replacement is probably the most economical choice.
Power supplies are rated by the wattage output. An old computer will have a 70 watt power supply. Today, they go as high as 500 watts. The average computer today uses 230 watt or 250 watt. If you are buying a new power supply, buy one with this rating, and you will be set to go with numerous attachments.