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5 Posts

06-16-2015

Tarrytown, NY

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T420 -- What does blinking power light mean?

2016-07-09, 12:21 PM

Now that it's summer, my T420 is back to not booting if it doesn't feel like it.

 

As before, I press the power button, and instead of doing anything, the power light starts flashing, one second on, one second off, forever or until I get bored and pull the battery out for a second or two.

 

I've gone through all the threads even vaguely related to it, which are full of all sorts of weird fixes that don't work for me  (I haven't tried the eye of newt ones yet), but none of them answers the obvious question:

 

What condition does the flashing power light signal?

 

It's obviously something that the firmware or hardware is designed to do under a specific set of circumstances, but so far no one (least of all from Lenovo) has mentioned what they are.

 

I've tried taking it to the repair shop (MicroCenter), but the problem is that it never shows the problem at the repair shop.   It seems like if it's in a perfectly temperature and humidity controlled space for a long time, like your average repair shop, the problem goes away.  Or it used to, anyway.  Since I haven't found a set of specific conditions that consistently trigger the problem, I can't show it to the shop.

 

There are a lot of things I like about the T420.  But I can't deal with a laptop that only works when it feels like it, and which has a problem that a lot of people share but the manufacturer isn't helpful with, so I think my next one (i.e., after I give up on this one) will not be a Lenovo.

 

 

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8981 Posts

01-13-2008

United States of America

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Re: T420 -- What does blinking power light mean?

2016-07-09, 23:31 PM

Hi,

 

My T420 does that - Power button LED one second on, one second off - when it's asleep.

 

Tapping the power button or Fn key wakes it up.

 

FWIW,

Z.


The large print: please read the Community Participation Rules before posting. Include as much information as possible: model, machine type, operating system, and a descriptive subject line. Do not include personal information: serial number, telephone number, email address, etc.


The fine print: I do not work for, nor do I speak for Lenovo. Unsolicited private messages will be ignored - questions and answers belong in the forum so that others may contribute and benefit. ... GeezBlog

 

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5 Posts

06-16-2015

Tarrytown, NY

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Re: T420 -- What does blinking power light mean?

2016-07-10, 11:39 AM
It's not asleep. It hasn't even powered up. And it does not respond to anything -- especially not the power button.

The sequence is: I remove the battery. Then I put it back in. Then I push the power button. And it blinks. And nothing gets it to stop blinking but removing the battery.

Note: I frequently use both sleep and hibernation (well, when the laptop is working.) Neither of them results in a blinking power light once it's finished going into sleep or hibernation mode.

This is some kind of hardware error code.

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8981 Posts

01-13-2008

United States of America

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Re: T420 -- What does blinking power light mean?

2016-07-10, 12:05 PM

I'm not suggesting it's asleep, at least not in a normal sleep state.

 

The T420 I'm typing on now continuously blinks the power button LED when in the sleep state.  The little green moon on the outside of the display does act as you describe.  It blinks whilst going to sleep.

 

From page 11  of the (English) User Guide - ThinkPad T420, T420i

 

The power switch stays lit whenever the computer is on, blinks when the computer is in sleep (standby) mode, and is off when the computer is off.

 

FWIW the Hardware Maintenance Manual - ThinkPad T420, T420i lists error codes starting on page 47.

 

Have you tried the last-resort BIOS reset?  Pull the CMOS battery and hold down the power button?  Since it's intermittent it doesn't really point to that, but maybe it's time for eye of newt.

 

regards,

Z.


The large print: please read the Community Participation Rules before posting. Include as much information as possible: model, machine type, operating system, and a descriptive subject line. Do not include personal information: serial number, telephone number, email address, etc.


The fine print: I do not work for, nor do I speak for Lenovo. Unsolicited private messages will be ignored - questions and answers belong in the forum so that others may contribute and benefit. ... GeezBlog

 

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5 Posts

06-16-2015

Tarrytown, NY

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Re: T420 -- What does blinking power light mean?

2016-07-13, 1:40 AM

The CMOS battery is the thing under the keyboard, right? So I'd have to disassemble the computer to get to it. Not a 3 minute fix. But I may try it at some point.

 

Would there be any point in replacing the CMOS battery?

 

Too bad computers don't come with reset buttons any more.

 

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8981 Posts

01-13-2008

United States of America

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Re: T420 -- What does blinking power light mean?

2016-07-13, 2:48 AM

If the CMOS battery was failing you'd see BIOS checksum errors or clock errors on boot.

 

Unplugging it is just a last-ditch way to reset things.  Given your stated symptoms I wouldn't really expect it to make any difference.

 

One easier thing you might try: if you can get it to boot to BIOS reset it to defaults.

 

Very much a long-shot.  Just another thing to try.

 

Z.


The large print: please read the Community Participation Rules before posting. Include as much information as possible: model, machine type, operating system, and a descriptive subject line. Do not include personal information: serial number, telephone number, email address, etc.


The fine print: I do not work for, nor do I speak for Lenovo. Unsolicited private messages will be ignored - questions and answers belong in the forum so that others may contribute and benefit. ... GeezBlog

 

Communities: English Deutsch Español Português Русскоязычное Česká Slovenská Українська Polski Türkçe Moto English

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1 Posts

08-15-2019

United Kingdom of Great Britain and Northern Ireland

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  • Message 7 of 9

Re: T420 -- What does blinking power light mean?

2019-08-15, 9:06 AM

My lights (power, speaker,caps lock) started flashing and wouldnt power on after I dropped my laptop.

 

I opened up the bottom cover with the 6/7 screws found the ram card and ensured it was pushed all the way home, As suspected I felt it move and click in place and after this the computer worked fine. The bang had obviously popped the chip slightly out from its mounting. 

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8 Posts

07-23-2020

Singapore

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Re:T420 -- What does blinking power light mean?

2020-12-12, 14:07 PM

I know ithe thread start 2015, any solution for this issue?

My T420 also showing the same symthom, power button LED blinking when I pressed the power button.

If I leave it blinking for about 8 minutes, it boot normally. However if I shutdown and pressed the power button again, it work boot normally no blinking.

My guess it is only happen when cold boot (have not use for a while). I check the BIOS battery still 3V.

Just now I pressed the "thinkvintage" button while the power bvutton LED blinking and it boot up but I'm not sure whether it is coincidence or not.

Need to try again another day to confirm.  

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1 Posts

01-25-2021

Hungary

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  • Message 9 of 9

Re:T420 -- What does blinking power light mean?

2021-01-25, 21:13 PM
Is there a solution yet?
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