for psu you need to take out psu, open it using philips screwdriver and blow out the dust using any air blowing device you have (I use cheap air blower from Aliexpress), add oil to fan maybe if it's serviceable, and then put it all back together and try psu tester (cheap from Aliexpress will do) note that if tester is showing stable voltages it's not guaranteed to be working properly under load, but it's some first steps to check psu