Lenovo ThinkPad T420s Troubleshooting

Your laptop fails to to turn on or show any signs of response.

First make sure the laptop does not attempt to power on at all; if you hear the fan or other lights on the keyboard or power button turn on then it may be the screen that is broken and you need to replace it; you can replace the screen unit using this guide. If it does not attempt to start then continue reading.

Make sure your power adapter is plugged into the computer properly, most laptops will have a light turn on for when they are charging. After it is plugged in wait a few seconds then attempt to turn it on. If this does not work then continue reading.

If there are no lights or other indicators showing the laptop is charging when the power adapter is plugged in then your battery may be faulty and unable to hold a charge. If this is the case then use this guide to replace your battery.

Another reason your laptop is unable to charge when plugged in is that the power adapter is faulty. You can purchase new adapters here.

The bottom of the laptop gets very hot or shuts down without warning.

Computers can overheat if there is a lot of dust in the fans or vents blocking airflow. To fix this, use a can of compressed air to blow out the dust or remove the fan entirely to clean it with a soft rag.

It is possible that the thermal compound that conducts heat may be dried up from use. You can replace the thermal paste on your GPU/CPU using the guide here.

Either you have one or more keys that are hard to press and/or don't type anything at all when pressed. Or perhaps your keyboard has stopped working entirely.

Sometimes the problem is as simple as a bit of dirt beneath the keys. This is especially true if it's only a few keys that are problematic. Clean your keyboard by turning your keyboard upside down and shaking any loose debris, as well as by using a compressed air can in between the keys. If your keys begin to stick, you may have to remove the keyboard and use cotton swabs in conjunction with rubbing alcohol.

If cleaning isn't the quick fix, then there is most likely a faulty connection. Your best option is to replace the keyboard unit; you can replace the keyboard using this guide.

The CD/DVD fails to read, or fails while burning a new disc.

If your CD/DVD drive fails while burning a new disc, it is likely that your optical drive’s firmware needs updating. To see whether your driver has new firmware available, visit the manufacturer’s technical support site.

If your optical drive fails to read a CD or DVD, first try cleaning the disk. If cleaning the disk fails, try a different disk. If the problem persists, it is likely that one of the lasers used for reading disks has failed. The easiest solution is to replace the optical drive.

The laptop doesn't produce any sound when headphones or external speakers are plugged in, or doesn’t recognize input.

First and foremost, check if it's muted! Also, make sure the volume is turned all the way up. If it's still not working, read on.

Sometimes, audio cables are large and bulky and needs an extra push to properly connect to an audio jack. Make sure your headphones, external speakers, or other device are plugged in all the way. Try another pair of headphones if the first one doesn't work. If you're sure they're completely plugged in and there's still no sound, keep reading.

It's possible that your laptop detects multiple audio devices, but hasn't switched to use the one that you want it to use. Go to your Control Panel, then to Hardware and Sound, and then to Sound. Now go to Manage Audio Devices. If you see the device you want your laptop to play sound from, double click it to set it to that device. If you don't, or if it was already set to the device you wanted and it still had no sound, keep reading.

It's possible that your laptop's sound drivers aren't up to date, leading to it not producing any sound at all. Use Window's Update to update your sound drivers. If after updating and rebooting your sound is still not working, read on.

Your laptop isn't muted, the sound is up, and still you're not hearing anything from your headphones. At this point, you need to replace your audio jack.