Help! My T420 is breaking keyboards.

[andrewferguson]

So this is a bit of an odd story, but bear with me...

Last November I bought a T420. It worked well for the first month but it had a sticky patch on the keyboard where the arrow keys were. In December I decided that the best course of action would be to clean the keyboard, so I removed the five or six keys around the sticky area, and cleaned the area underneath with a damp cloth. However, when I put all the keys back on, the T420 had stopped working. It refused to power on, but sometimes - very rarely, mind - it would power on, only to power off again after any time between 5 seconds to 10 minutes. I feared a broken motherboard but because I had been cleaning it when the fault developed, I began fiddling with the keyboard. To my surprise I found that something had gone *really* wrong with the keyboard.

During one of the brief times that it booted for more than a few seconds, I dropped into a shell session and began to press keys on the keyboard. To my surprise I found that many of the keys had "remapped" themselves, with one key resulting in one or more multiple keypresses from other keys. In particular, pressing repeatedly on the arrow keys – the area which I cleaned – would cause the ThinkPad to instantly power off.

A friend kindly let me test my theory by borrowing the keyboard of their T420 and their keyboard worked fine in my machine – all the issues were gone. I pulled out the broken keyboard, bought a "new" one off ebay (it was from a private seller, but they claimed it was new) and thought nothing more of it.

Today, the T420 stopped working. Again. It started when I noticed that the Caps Lock light was always on, and pressing the Caps Lock would only make it go brighter. Then it acted as though the middle mouse button was always pushed down, so moving the mouse scrolled the active window. I restarted it and it then acted like the middle mouse button didn’t work at all. I restarted it again, and this time it wouldn’t power on. The symptoms were very familiar. The majority of the time it would not boot, but sometimes it would boot, often only to power itself off again after about 5 seconds. Very occasionaly it would not power itself on and let me boot into the OS. This time, however, once booted into the OS (I run Debian Linux) it would not power off, and would function normally (with the exception of the middle mouse button, which remains non-functional). I've taken everything non-essential out (excess RAM, hard drive, ultrabay caddy, wireless card, battery) and the problem doesn't go away.

Has anyone had a similar experience, or would know what could be causing my troubles? It could just be another bad keyboard, but I am reluctant to buy another keyboard only for it to break in a few months time…


[Aside: for the curious, I have included a map of which keys on the first keyboard were remapped. But note these are only the visible characters; some keys are pressing other non-printing characters when pressed, which I can't detect].

Escape Key maps to z
F5 maps to enter or return
F6 maps to comma
Backtick maps to backtick, but maps to ~ if shift is pressed, rather than ¬
g maps to vg (a v followed by a g)
h maps to mh
apostrophe (') maps to \'
# maps to \'
\ maps to x<
left arrow maps to n and some control keys
the other arrow keys do not work at all (repeatedly pressing them has caused the system to power off)

[axur-delmeria]

Having two bad keyboards isn't rare. My dad's X220 (which uses the same keyboard as the T420) is now on its third keyboard.

It sounds like some wires got shorted/grounded in the old keyboard. Also check the keyboard connector for any physical damage.

[andrewferguson]

That's good to know.

Before I buy another keyboard, I'd really like to nail down whether the issue is with the keyboard or the motherboard. This is tricky because the power button is on the keyboard.

Is there a way to power on the T420 without using the keyboard? Or even a BIOS setting which makes it turn on as soon as it gets power?

[TonyJZX]

A few things... I have rarely seen keyboard failures and I might have seen literally thousands of classic Thinkpads. I myself have over a dozen and I've had one failure and its like as this fellow describes... a certain section fails and then the whole lot.

And its a pain to see as this keyboard was in perfect conditon.... so I might transfer the keycaps over to a worn keyboard.

Also I feel that classic keyboards are expensive. I think they are $40 usd each new? Perhaps more now that the classic era is now coming to 10yrs ago!

So I feel that if your laptop is killing $40 keyboards regualarly...

[axur-delmeria]

Is there a way to power on the T420 without using the keyboard?

1. Grounding Pin 19 on the keyboard connector.
2. Series 3 Mini Dock and Mini Dock Plus have a power button that can turn on the laptop. The Series 3 port replicator doesn't.

[andrewferguson]

Ah! I never thought of the dock. I can get that for considerably less than the keyboard, so I may go down that route (I don't trust myself to not accidentally short something out if I try pin 19).

On my previous Dell Laptop you could boot into a sort of checkup firmware, where it ran tests on various aspects of the hardware. Is there anything like that (even a bootable CD image) for ThinkPads? Specifically to test the motherboard.

[axur-delmeria]

There's this: https://support.lenovo.com/kr/en/downloads/ds025448, though TBH I haven't tried it yet.

[TPFanatic]

In my experience the keyboards, especially Chicony, are incredibly fragile electrically. The T520 in my sig came with a super worn keyboard that had the mute LED always on, and pressing that would shut down the laptop. Two more of my CS09 Chicony keyboards developed nonfunctioning Delete keys.

[Yukikaze]

Lovely, one more reason why T420 and old stuff are BAD for new users.