No Power On Computer: Check power cable, it might be possible that the cable has been damaged internally. you can test the power cable using a multi-meter by connectivity check.
Check power buttons & power pins.
Check power button of your cabinet is working or not, you can check this by shortening the power pins on the motherboard with a screwdriver take a normal screwdriver, locate the two power pins on your motherboard and then touch both of them with your screwdriver for a second. if your computer power ON and boot normally then the issue in with your PC. cabinet power button and if it does not then you can go through the next step, also make sure that the power pins connector of your power button is fitted properly and tightly on your motherboard power pin.
It might be possible that your SMPS and power supply has gone faulty. if your SMPS is damaged than your PC wan;t start. To test the SMPS short the indicated pins of 20+4 motherboard/ATX connector and turn on the power to see if the SMPS start or not. If the SMPS fan does not start or the SMPS is not powered ON then it is damaged. here, the only fix is to replace your SMPS with a newer one. if the SMPS start and it’s fan is shipping then you follow the next step given below.
IMPORTANT :- Always use a good quality spike guard or spike buster power strip for your computer to protect it from voltage or current spikes.
It might be possible that something is getting short on your cables or motherboard. here, you remove all the cables except the main power cable(24-pin) of your motherboard and start your PC. if the SMPS start POST screen is displayed then you might be having some faulty cables. inspect all the cables one by one and replace the faulty one.
A faulty motherboard can also has cause of this problem . if the SMPS and all cables are OK, then it might be possible that your motherboard has gone damaged somehow take it, to the service center and get it inspected, repaired or replaced.
In some motherboard it can happen that a discharged or loosely fitted CMOS battery won’t allow PC to start. so make sure that your BIOS or CMOS battery is working fine and is properly fitted in the motherboard.
Make sure that the voltage you are getting in your home or office is proper. This is because low voltage can also prevent your computer from powering ON. you can test the voltage in your home by using a digital multimter.
If your computer is getting power an all fans are spinning but your pc wan’t boot then it canbe an issue with ram. test whether your ram is working fine and if it is, then just put it again in it’s slot properly. before inserting RAM in the motherboard slot just clean the slot and remove and dust from it.
Power cycle of the Laptop
The first thing that you should do when your laptop won’t turn on is to power cycle the laptop. To perform this just follow the bellow mention steps.
Turn off the laptop and remove the power adapter or charger.
Remove the laptop battery.
Power button for 30 to 60 seconds.
wait for a 5 minutes.
Insert the laptop battery in its place.
Turn On the laptop.
NOTE:- For performing above power cycle steps your laptop battery should be charged.
If you are starting Laptop from the battery and the adapters is not attached then it might be possible that your battery is completely discharged or is not getting charged. If the battery is not getting charged then you should replace it with a new battery.
Check Power Adapters
Check whether your laptop power adapters is working properly and providing the appropriate voltage. you can check this with the help of a Digital Multimetre.