Thinkpads Forum

Considering I can get one on eBay for under $200 with a buy it now, i'm not willing to put a terrible amount of effort into this machine.

That said, it's been running 24/7 for many years now and never had a problem until today. Woke up, went to use it, and found it was shut off. Turned it on, saw two of the indicator lights come on, and it seemed to detect the CD drive, then just shut off, just like that.

Figured I accidentally unplugged the power cable - nope. Power cable is firmly seated.

Did some googling and did the 1 second + 30 seconds trick to reset and static electricity. No solution there either.

Tried all sorts of booting with and without battery. Nothing.

The only thing I can think of, other than if the motherboard finally bit the dust, is that the battery I was using with it was completely dead. As in, you would get between 2 and 5 minutes of life when the cord was unplugged before it gave you a critical battery warning and shut off. It says plugged in virtually 100% of the time. When I left it last night it was plugged in and running.

I ordered a new battery and CMOS battery from Amazon express shipping just to be safe. I did not suspect the CMOS battery to be an issue, but one particular google result pointed to needing to replace it, so I bought it just in case.

is it still worth it at this point though? Or is my T420 toast?

Hopefully I won't have to buy a new Thinkpad and swap drives out

Have you tried another power adapter?

bit_twiddler wrote:Have you tried another power adapter?

I've tried a 95w (the one i usually use) and a 65w which I mainly use with my X201.

I've tried the X201 on the 95w charger so it seems to be good.

To further add to the mystery - left the CMOS battery unplugged for about half an hour. Tried turning it on again and the screen lit up and stuck with the Bluetooth light on. Realized the CMOS was unplugged, turned it off, re-attached CMOS battery, and now it turns on, shuts off, and tries to turn on again the moment you connect AC power.

Clearly something's weird with this T420! Also i'm increasingly afraid it means this T420 is toast. I'd hate to have to replace it. but, whatever.

You could just replace the motherboard!
A lot cheaper...

They're really cheap now. Hardly worth your time to do anything else.

Here's one with nvidia (which won't work for me but might for you)

http://www.ebay.com/itm/Lenovo-ThinkPad ... SwBnVW--pb

I'd make sure that whatever you get has a 1600x900 screen, but that's just a personal preference.

Next time that RMSmajestic makes it over from the "Beautiful Country" (Chinese for the US, "Meiguo") to the "Middle Kingdom"
he can straighten out all of those nasty bugs that they're having with FHD displays on the T420, and
you'll be completely spoiled.

There's a bios setting for powering on the machine the moment it's connected to power - perhaps it's the default setting and you've stumbled onto it by removing the cmos battery.

Remove ALL of the peripherals and see what happens.

First, thank you very much to all for the responses. I greatly appreciate all your help and thoughts.

I had a long reply but I hit the back button accidentally and wiped out so I apologize this post will be more succinct.


jaspen-meyer Very interesting! Replacement CMOS battery will be here Wednesday so I will hope for the best then. I already tried booting without battery, RAM, SSD, hard drive and optical drive.

bit_twiddler You know I have been checking in from time to time on the status of the FHD T420's. Nvidia would be fine for me but I think I am actually going to hold out for a T420s as the USB 3.0 would be a seriously welcome upgrade.

RealBlackStuff If the CMOS battery doesn't solve it I think this is the plan, my man!

Posted from my long-neglected X201 running a fresh Xubuntu 16.04 by the way.

My experience with T500 and CMOS battery is that if you disconnect the CMOS battery, the computer, upon receiving AC power, will power itself on and power cycle itself twice. That is a normal behavior.

TPFanatic wrote:My experience with T500 and CMOS battery is that if you disconnect the CMOS battery, the computer, upon receiving AC power, will power itself on and power cycle itself twice. That is a normal behavior.

OK, thanks for this.

Pretty sure the motherboard is toast anyway.

I always leave it running and never let it sleep (may have contributed to its death) - I didn't see it before it died but my wife who walked by it and looked at it noticed all my open windows were quickly rotating thru each other, almost as if alt-tabbing extremely quickly.

When hearing about it I couldn't help imagining what could possibly cause such a thing. I thought GPU failure but it's integrated into the CPU, however it's not worth worrying about now, though I do really wish I saw what it was doing or if I was getting hacked and the laptop dying was a coincidence

It's unfortunate I didn't get to see for myself what happened, she thought it was a screen saver, I was dead asleep from a long day's work anyway!

I would suggest a T420s as a replacement. It's not worth getting a new motherboard. Simply get a replacement T420 and transfer your RAM and HDD to the new machine. That way you can troubleshoot your dead T420 while still having a functional T420.

Dumb question but if I see an i7 motherboard can I swap that into this dead t420?
I assume they're all interchangeable but wanted to check first.

There is no such thing as an i7-mobo in a T420 (only in T420s which has soldered CPUs).
In T420 any T420-mobo and any i3-2xxxM, i5-2xxxM or i7-2xxxM will fit. Check the HMM.
If you had Intel graphics and now want discrete graphics, you also need a different heatsink.
The rest of your old parts is transferable.

RealBlackStuff wrote:There is no such thing as an i7-mobo in a T420 (only in T420s which has soldered CPUs).
In T420 any T420-mobo and any i3-2xxxM, i5-2xxxM or i7-2xxxM will fit. Check the HMM.
If you had Intel graphics and now want discrete graphics, you also need a different heatsink.
The rest of your old parts is transferable.

Ah I see, I didn't realize the T420 had a socketed CPU actually.

Wouldn't there be a good chance my old CPU is fried though? I'll be on the lookout for a motherboard I can use though!

The issue you describe doesn't sound like the fixable issues I'm aware of: won't turn on at all (power button pressing to release static), stuck on ThinkPad splash screen (USB pin short), turns on but stays on not booting (bad or incorrectly seated RAM).

Cheapest option to get back to a working T420 would be to look for a working T420 on eBay with a broken screen. You could then buy that machine, swap in your screen and peripherals and you're off and running. You might have some spare RAM, disk, battery, keyboard, DVD etc. to sell off to further reduce cost.

I hear you but it seems a lot more expensive to get a working t420 and swap the parts over. I grabbed a motherboard last night on ebay for $20, hopefully my cpu is still in okay shape.