Why won't my T420 boot unless keyboard is removed? (Solved)

[excal32]

I have made a few threads here so some of you probably are familiar with what I'm struggling with... if not my T420 died all of a sudden one day, tested it by removing every component until it kept not booting and determined the motherboard was bad. Well I went ahead and got a new motherboard and installed it today.

Okay so I got a new motherboard installed in my T420 and was met with a laptop that doesn't boot again. After nearly giving up when it wouldn't boot, I decided to rip out of the keyboard and leave everything else in. Lo and behold it booted to windows instead of dying before the "Thinkpad" BIOS screen!

The other issue is since I don't have a thinkpad keyboard hooked up, the only way to power it is unplug the CMOS battery and then plug it in with AC, then plug in my USB keyboard and use that. I set it to auto power-on when AC is hooked up, but that didn't happen when I tested it out.

Do you guys think if I buy a new keyboard that'd solve it? Sitting a USB keyboard on top of a bare thinkpad is pretty sad and no trackpoint is torture!

Is there any chance it's not the keyboard?

[theterminator93]

Well, if the motherboard is different and NOT having the keyboard connected is the only change between booting and not booting, it's a pretty good chance that's the problem. Could be a bogus power button circuit or something; never know really.

[excal32]

Well, if the motherboard is different and NOT having the keyboard connected is the only change between booting and not booting, it's a pretty good chance that's the problem. Could be a bogus power button circuit or something; never know really.

The other motherboard didn't boot either with it would get stuck with the keyboard's power button light on and the Bluetooth light would stay on. With the new motherboard the screen would turn on for a split second then go back off.

I'd be pretty annoyed if I did all that just to realize the keyboard was the only thing wrong! Well, i have some new thermal paste on my CPU, so maybe it's not all bad

Either way I'll assume it's the keyboard, buy a new one, and hope that does it, thanks.

[Brad]

I had another ThinkPad (X230) that ran for a short time then froze on each boot. I usually could run a recovery then on restart it would freeze. I replaced two motherboards with the same problem. After examining the keyboard there was a piece disconnected from the ribbon cable. I replaced the keyboard and all is well.

My .02c

Brad

[excal32]

I had another ThinkPad (X230) that ran for a short time then froze on each boot. I usually could run a recovery then on restart it would freeze. I replaced two motherboards with the same problem. After examining the keyboard there was a piece disconnected from the ribbon cable. I replaced the keyboard and all is well.

My .02c

Brad

Brad I think you were right. My old keyboard was pretty worn out. I used it with a USB keyboard and the internal one disconnected until today, I got a new replacement keyboard for the T420 and dropped it in, everything seems to work perfectly again, plus the new keyboard is a great feeling, the old one was so worn and dirty

[Brad]

Great to hear!



Brad