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[LENOVO THINKPAD T420s] Completely erratic behaviour of my laptop (random crashes and random boots)

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Feynman81
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Joined: Thu Mar 15, 2018 4:58 pm
Location: Milan, Italy

[LENOVO THINKPAD T420s] Completely erratic behaviour of my laptop (random crashes and random boots)

#1 Post by Feynman81 » Thu Mar 15, 2018 5:12 pm

Hi guys,

I bought this laptop as per description, I bought it refurbished since I wanted a cheap and light laptop to carry around.

The laptop worked flawlessly for 8-9 month then suddenly it started to have problems.

At the beginning it started to freeze when using it (screen freezes and that's it), I had to power it off with the power button and then restart it.

After 2-3 months of this it started to refuse booting, sometimes it boot, sometimes it doesn't; all the LED are on (power and HD) but the screen is off, it doesn't even show the BIOS screen.

The laptop boot about 30% of the times I try to start it, the other 70% nothing but the LED as described above, sometimes it freezes during use but again all of this is completely random, I have no idea why it happens, sometimes it freezes on the "LENOVO" boot splash screen too. It's just completely random.

What I know is this:
- I'm pretty sure it's not the LCD panel, I tried to connect an external monitor but it's the same erratic behavior all over again
- I'm pretty sure it's not the HD since I tried with a new one, same story...
- According to he LENOVO user manual it can be one of these two things (in order of probability): 1 RAM Failure - 2 Motherboard failure.

Well, I hope it's the RAM of course (because it's 30 Euros and easy to change), if it's the MB I can pretty much kiss it goodbye because it would be cheaper to buy an other one than buying the MB.

Now it has been working for two hours running Memtest86+ to test the RAM, I'm already at the second pass but it detected no errors "Pass complete, no errors, press ESC for exit".

Is memtest infallible? Should I try buy a new RAM stick and try it anyway even if memtest is ok? What's your opinion?

Thx.

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Re: [LENOVO THINKPAD T420s] Completely erratic behaviour of my laptop (random crashes and random boots)

#2 Post by RealBlackStuff » Fri Mar 16, 2018 6:23 am

Is there hot air (or any air) coming out of the fan exhaust?
When is the last time you cleaned the fan and replaced the thermal paste between CPU and fan?
Could overheating be the cause?
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Feynman81
Posts: 2
Joined: Thu Mar 15, 2018 4:58 pm
Location: Milan, Italy

Re: [LENOVO THINKPAD T420s] Completely erratic behaviour of my laptop (random crashes and random boots)

#3 Post by Feynman81 » Fri Mar 16, 2018 2:21 pm

RealBlackStuff wrote:
Fri Mar 16, 2018 6:23 am
Is there hot air (or any air) coming out of the fan exhaust?
When is the last time you cleaned the fan and replaced the thermal paste between CPU and fan?
Could overheating be the cause?
Hi, thanks for the answer.

Yes the air seems to be blowing out from the outlet on the side regularly.

I never cleaned it to be honest, the temperature during the memtest were 66-69 °C, they seem normal to me. Even today I have to restart it 3 times to have a successful boot. This is really weird...

turomini
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Re: [LENOVO THINKPAD T420s] Completely erratic behaviour of my laptop (random crashes and random boots)

#4 Post by turomini » Sun Apr 01, 2018 1:07 pm

I think ram memory is more of a work/no work, not a occasional not work part. Of course odd things can happen, and there can be bad sectors in the ram, which is what you use memtest to check for.
Before you buy any, its usually more practical to remove one chip, or swap them. Sometimes just pulling them out and putting them back in can help. But generally if it passes a long enough memtest run, then most people feel confident that they are working. Memtest works by testing random sectors of the ram, there is no guarantee that it will check ever sector, which is why people run it for a very long time to check everything.

I'm pretty sure a bad fan doesn't cause a no boot on these laptops, just an error message on boot or overheating. Its not exactly easy to overheat these laptops either. I've reached 90C+ a few times without any problems. Mainly it starts to throttle and get extremely slow.
Hard drives don't get looked at until after the splash screen.

My initial reaction is the gpu if you have the nvidia gpu.
What is the tempature of the gpu anyway?
I haven't heard much about the T420s gpu having issues, but I've heard other brands that had a lot of issues with them. I'm using the T420s with the nvidia gpu and it can get hot easily, but its not an issue when you aren't using any graphics intensive programs.
If you do have the nvidia gpu, good luck finding a fan for this laptop. They are out there but most of the heatsinks are for the intel only graphics version of this laptop.

The other out of the box thing I can think of is a lose connection inside the laptop. I had a lose screen connector on a Toshiba laptop that caused random issues like this, but I quickly fixed it since I had just had it apart anyway.

When it doesn't boot, what happens? You say the hard drive and and power lights are on, but not the screen? Any sounds?
On my T420s I think the mute buttons blink, I hear something else active, etc. I restart my laptop once a month, I can't remember exactly what it does when it turns on.
Compare it to the times it does turn on properly.

Also, what is your temperatures when the laptop is running?
https://www.staff.uni-marburg.de/~schmitzr/tpfc.html
I use the tpfc_v063.zip but 062 may work.

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