ThinkPad released in 2011. This version of the T420 is thicker than the T420s and lacks integrated USB 3.0. The T420i uses the same chassis, so most T420 repair guides work interchangeably.

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Power / Startup Issue?

Greetings all,

I have a Lenovo ThinkPad T-420, and it appears to be in good condition. (I found it in my friend's garage and he said I could have it!) But even with a "good" working battery?...or plugged in with a "good" working power adapter it won't power on. its as if there's no power to the device even though there IS a good battery and power supply(and I know the battery and power supply are good because I have ANOTHER T-420 that they came from!) )Its not a bad looking laptop, and I would like to use it, but if its not working I don't know what to do next. Can anyone shed some light on this issue for me? Or is there someplace I ca ship it to be repaired?

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1 Answer

Most Helpful Answer

Hi,

Try a "power reset" and see if that works.

Remove the charger and the battery from the laptop.

Press and hold the Power button on the laptop for 30 seconds to discharge any residual power from the laptop.

Connect and turn on the charger to the laptop (leave the battery out at this stage) and try to start the laptop.

If it starts OK and there is an OS installed, allow it ot boot all the way to the desktop, let the HDD activity settle down and then shutdown the laptop in the normal manner.

When it has completely shutdown, switch off and disconnect the charger, reinsert the battery, reconnect and switch on the charger and turn on the laptop.

If it starts, allow it to boot all the way to the desktop, allow the HDD activity to settle and then check the charge status of the battery. If it is charging, allow it to fully charge before switching off the charger and disconnecting it from the laptop.

Also check the voltage in the "backup battery" just in case it is faulty and corrupting the BIOS settings

Here's a link to the service manual for your laptop. Scroll to p.38-39 to view how to test the backup battery

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