10-28-2018 04:38 PM
This just started happening.
My T420s won't turn on using ON button -- it blinks a bit but nothing happens -- but it will turn on if I push and hold down the down-arrow button. The only problem is I have to keep holding the down-arrow button down. As soon as I lift off the down-arrow button it crashes.
Wierd I know. Any ideas?
I mainly want to use this laptop in the expansion tray with an external monitor so I am thinking of trying to put a pad on the down arrow button that a closed top will hold down but this is a bit of a kluge...
10-28-2018 05:00 PM
OK ... first I gotta know .... what made you try holding down the down-arrow key?
Does the T420s have the "paper clip reset" hole on the bottom?
This is the procedure for an X1: https://is.wfu.edu/help-articles/hard-reset-for-lenovo-x1-carbon/
My T440s and T480 both have the hole....
the hole is not in the same place on all the machines of course, but you get the idea.
Or maybe you already tried this trick?
10-28-2018 06:56 PM
Not finding the reset hole...
I found the down arrow on randomly, touching the computer randomly and noticing it came on somehow, and then looked closer and found that the down arrow did it.
I'm not making this up!
There are some reset proceedures for the T420s out there, pushing the on button 11 times etc. without it plugged in. I have tried that...
10-28-2018 07:08 PM
I didn't give the information correctly.
I have to hold down the power button AND push the down arrow. Then it turns on. As soon as I let up on the down arrow it shuts off...
10-28-2018 07:30 PM
Amazing that the down-arrow key somehow makes it function.
I found the "Hardware maintenance manual" ( HMM ) for the T420s and I may have missed it, but it does not appear the T420s has the "paper clip reset" function.
I'm out of ideas, but the HMM is available here, and might offer some tips:
11-14-2018 05:01 AM
Thanks for all the ideas. Turned out the down-arrow trick was itself flaky, and eventually stopped working. I have found a new system board on Ebay for $75 and have ordered that...