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T520 lid sensor problems

T400/T410/T420 and T500/T510/T520 series specific matters only
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mitchW
Posts: 7
Joined: Wed Jun 27, 2012 4:27 pm
Location: Celje, Slovenia

T520 lid sensor problems

#1 Post by mitchW » Thu Nov 19, 2020 9:06 pm

Hi,
I bought an used ThinkPad T520 that was supposed to be working w/o problems.
When I brought it home, the screen was dark and the keyboard wasn't responding. If I moved the screen up or down, the image came back for a second. No luck with returning it to seller, as he claimed that the laptop was 100% working when he was using it.

So, I took off the keyboard then and disconnected the LED/Camera/Lid Sensor cable. Now the laptop worked flawlessly, but of course I was missing all the disconnected stuff.

I then decided to buy another LED/Camera cable and replace it. Since I am from Europe, the only part that was reasonable priced was an used one, so I got that one. I then replaced it, and I was careful to route it exactly as it was before, etc.

The laptop worked flawlessly for 2-3 days, I reinstalled Windows, etc., but then I got random hibernate events, and the laptop stayed on for less than few seconds before it registered a close event and went into hibernate. I somehow managed to change lid close action to "none", but now I got screen that flickered every now and then. I put it to standby and after an hour when the laptop woke, I just had an black screen. I had to unplug the LED cable to get it back. I then tried the original (broken) cable and it seemed to be working fine, but that cable wasn't connected to camera or LED board.


TL:DR, now the question: are those cables both broken or damaged someway and are just a bad quality part, or am I having a problem with a logic board, or something completely different? Disconnecting the cables always made the problem go away.

kfzhu1229
ThinkPadder
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Joined: Tue Sep 22, 2015 10:59 pm
Location: Toronto, Canada

Re: T520 lid sensor problems

#2 Post by kfzhu1229 » Thu Nov 19, 2020 10:36 pm

The lid sensor is a small board with a transistor mounted on the left side of the screen bezel for every T510-T530.
Perhaps first try taking off the screen bezel and see if anything improves?
Then try putting a piece of magnet close to it and away from it, it should respond to lid close and open exactly as you move your magnet.
Also, unplug, clean (with contact cleaner) and reseat the screen cable. The screen cable carries a lot of current and can get oxidised as well.
UNPLUG the battery and charger when you do that. the cable carries 10-19V even if the computer is off!
Dell Lat CP MMX-233 64mb 40gb W2k
600 PII-266 416mb 40gb WXP
T23 PIII 1.13ghz 1gb W7
Lat D830 X9000 8gb 160gb WUXGA Ultrasharp fp W10
T530i 15.6" i7 16gb fp W10
UXGA:
A30p PIII 1.2 1gb W7 (IDTech)
T43p 2.26 2gb fp W10 (Sharp)
Lat C840 P4-2.5 2gb 60gb W7 (Ultrasharp)

mitchW
Posts: 7
Joined: Wed Jun 27, 2012 4:27 pm
Location: Celje, Slovenia

Re: T520 lid sensor problems

#3 Post by mitchW » Fri Nov 20, 2020 9:39 am

Hi, yes the hall sensor is a 3 pin SMD device mounted on a small PCB on the left side of the LCD.
Taking off the bezel didn't seem to help in any way.

If I bring the magnet close to it, it turns off the LCD.

The connector was cleaned with professional contact cleaner as well with a fibreglass brush.


Should I order a new unused cable or is there a chance that is something wrong on a mainboard?

mitchW
Posts: 7
Joined: Wed Jun 27, 2012 4:27 pm
Location: Celje, Slovenia

Re: T520 lid sensor problems

#4 Post by mitchW » Sat Nov 21, 2020 8:30 am

I got the schematics for this logic board, and I measured pin 7 on the LED/Camera connector which is LID/SENSE pin.

It is being held to a 3.3V, but when the screen flickers, the voltage briefly dips to 2.7V.

Anyways, I ordered a brand new cable and we will see if this solves my problem :)

kfzhu1229
ThinkPadder
ThinkPadder
Posts: 1776
Joined: Tue Sep 22, 2015 10:59 pm
Location: Toronto, Canada

Re: T520 lid sensor problems

#5 Post by kfzhu1229 » Sat Nov 21, 2020 10:46 pm

Well I suppose a cheap way to fix is just wire the pin directly to 3.3V power supply on the board. It will make the lid sensor not work anymore but hey I think it's a small tradeoff to make.
Dell Lat CP MMX-233 64mb 40gb W2k
600 PII-266 416mb 40gb WXP
T23 PIII 1.13ghz 1gb W7
Lat D830 X9000 8gb 160gb WUXGA Ultrasharp fp W10
T530i 15.6" i7 16gb fp W10
UXGA:
A30p PIII 1.2 1gb W7 (IDTech)
T43p 2.26 2gb fp W10 (Sharp)
Lat C840 P4-2.5 2gb 60gb W7 (Ultrasharp)

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