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porkpiehat
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Posts: 11
Registered: ‎10-17-2018
Location: NL
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Message 1 of 10

Yoga 500 powers up but LCD is off

Strangest thing.. our Yoga 500-14IBD just stopped booting out of the blue. Yesterday it worked fine, this morning it would not boot anymore. It powers up, but it stays black. I can't find any similar problems unfortunately.

 

When pressing the power button, the power LED lights up, the keyboard backlight lights up and the HDD and cooling fan start spinning. The display stays black and does not illuminate. After +/- 3 seconds, the keyboard backlight is dimmed off, while the HDD and fan are on. That's it. It stays in this state for minutes on end. It almost sounds like it actually boots, but just no display.

 

When I press and hold the power button, it gives a long beep (+/-3 seconds), and then powers down.

 

This happened out of the blue, no warnings were given. I can't seem to get it to boot again. What I already tried:

- Reset button (10 and 30 seconds). After pressing it for 3 seconds, the system powers up with the same behaviour. Nothing happens when I hold it longer, nor when I press it when the system is powered up.

- Disconnected the battery. Also tried to boot on only the adapter, with the battery disconnected.

- Disconnected the battery and CMOS battery

- Reseated the DIMM and LCD connector

 

The beep indicates that the BIOS is fine, and by the sound of the HDD and fan I would say it actually boots into Windows 10. Just the LCD is not doing anything. I can try tomorrow to connect it to our TV with an HDMI, but we of course want to be able to use it as a laptop again.

 

Any thoughts on this? Help is greatly appreciated.

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Message 2 of 10

Re: Yoga 500 powers up but LCD is off

My first question involved an external monitor so I will be curious as to what the TV does.


Rich


I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo.
porkpiehat
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Message 3 of 10

Re: Yoga 500 powers up but LCD is off

I just connected it to the TV via HDMI and voilà, it booted just fine. It finished some Windows updates and I could log into my account. But still no LCD..

I'm trying to find out now if Windows can identify any errors with the LCD, or even recognise it. Keep you updated.

 

 Update: Nope. The LCD is not listed in Device Manager. Diagnostics does not find anything wrong, and all drivers are up to date according to the Lenovo Service Bridge. Multiple reboots did not bring back the LCD. Also tried to switch displays with Win + P, no success. Interestingly, the touch screen is still listed under Human Interface Devices and actually still works!

 

I guess reinstalling the system is not suddenly going to fix it. But then what..? Could it be that the LCD connector just suddenly gave up? I think that would be bad for a laptop that's hardly 3 years old and has been used only moderately.

porkpiehat
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Message 4 of 10

Re: Yoga 500 powers up but LCD is off

No one?

 

I find it strange that the LCD just suddenly went black, without previous indication of failure. I think it comes down to either of these 4 options: the LCD unit, the cable, the GPU, or a software/BIOS problem.

LCD Unit: seems strange that this suddenly stops altogether, because it gave no warnings like flickering, fading, dead pixels etc. that I commonly read about.

GPU: HDMI output still works, so this is fine.

Software/BIOS: If any, it would be non-OS related since it does not even show the splash screen at boot, before booting into Windows. I did not find anything in the BIOS (and it is up-to-date).

Cable: from the Hardware Maintenance Manual, I found that there is one multicable from the mainboard to the LCD unit that connects the digitizer, the LCD and the camera. Since the digitizer still works, the connector to the mainboard and at least a part of the cable are still intact.

 

On the Lenovo Support I did find cable spare part listed (P/N: 5C10H91193, W P/N: 450.03R01.0011), but of course it's useless to order it without being certain that this is the cause.

My next guess is to disassemble the LCD unit and re-seat the LCD cable there, though with little hope. I would have expected signs of a bad connection, like flickering, bad colours etc.

 

Anything I could still have missed, before I start disassembling?

porkpiehat
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Message 5 of 10

Re: Yoga 500 powers up but LCD is off


@porkpiehat

Anything I could still have missed, before I start disassembling?


Thoughts? Help is greatly appreciated.

Community Moderator
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Message 6 of 10

Re: Yoga 500 powers up but LCD is off

I'm assuming you have checked the brightness sliders under your power plan in Windows, correct?  We've heard from some users who had either the "plugged in" or "on battery" sliders moved to 0 following a Windows Update. There's also the "project" setting under Windows Action Center that can get stuck. 

 

Though the lack of a splash screen at boot has me suspecting the panel or the cable.  Next time you boot without an external monitor attached, get really close to the laptop's screen with a flashlight and see if you can detect any faint images. 


____________________________________
I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo. I love beer.
porkpiehat
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Message 7 of 10

Re: Yoga 500 powers up but LCD is off

Thanks for the reply.

 

I did the checks in Windows. I re-installed the graphics drivers and checked again for updates with the Lenovo Service Bridge, nothing. It does not even show up under Monitors in the Device Manager, only the TV is listed, so I think the LCD is not working at all.

 

With the flashlight test I could not even detect the faintest light in the LCD. It almost feels like if the power connector simply broke/disconnected. The touch digitizer and webcam still work.

I will disassemble the LCD unit after the weekend, test all the tracks on the cable and if it's fine clean and reconnect it. If that does not work I think the only option is a new LCD panel, which I already saw for 50-80€. It's a pity, but still affordable.

Community Moderator
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Message 8 of 10

Re: Yoga 500 powers up but LCD is off

Keep us posted, if you don't mind. 


____________________________________
I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo. I love beer.
porkpiehat
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Message 9 of 10

Re: Yoga 500 powers up but LCD is off

I have not found the time to disassemble the LCD, I want to have plenty of time to do so.Hopefully tonight.

 

I'll keep you posted for sure!

porkpiehat
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Message 10 of 10

Re: Yoga 500 powers up but LCD is off

It's been some time, but yesterday I finally had time to fully disassemble the laptop.

The service manual states that everything (hard drive, memory, touchpad) up until the main board has to be disassembled before the display unit can be disassembled. It seems however that everything can stay intact, except for the cooling fan unit, before the display unit can be removed. Waste of time..

 

But most importantly: after I wiggled and reseated the display cable and minimally reassembled the laptop for a test run, the display worked fine again! It failed again when tilting, so my suspicion of a faulty cable seems correct. At least I'm not going to take the risk and replace it anyway now that it's disassembled. It only costs a few euro's online (in my case LC41 450.03R01.0002 REV:A02, but it seems that versions .0001, 0002 and 0003 are the same).

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