Jolla Tablet LCD error
 

A few days ago, I browsed a bit on the Tablet when suddenly it froze.
Being a bit tired, I just long-pressed the power button to switch it off and went to sleep.
The next morning, I booted it up and the web page I was looking at was still a bit visible, also the screen flickered badly. It was pretty cold that night (with the window opened), this could be of some importance, as well.

Here's what I've tried:

• Put the tablet in a warm place for all further actions
• Let the battery drain as much as possible, switched on again and again until it shut down (or after it didn't boot completely)
• Playing one of those "fix my burned in pixel" videos for about an hour. Didn't find one to cover all pixels, though, even 4:3 ones didn't do that for some reason.
• Resetting the device (since it wasn't visible when booting – but that turned out to be just because the screen was too black to notice)
• Pressed on a few areas a bit more than I was comfortable with before turning on the display

None of these things had the desired effect.

After a few days of being plugged in, the web page isn't visible (or at least readable) anymore. The "burn in" started getting better at the center of the screen. I assume that's because the display turns on once in a while showing the lock screen (brighter in the center) when plugged in to tell me it's full (normally pretty annoying). The flickering is still there, mostly visible on non-black or non-white areas. While it seems to be less bad, I'm not 100% sure – it's still too bad to really enjoy using the device anyway.

I've now written a small app switching between red, green, blue, black and white relentlessly, because that was actually less work than getting a video like mentioned above playing on the whole screen. I'll let it run for a few hours, but am not very hopeful it'll work. But I will write updates here either way. If it does work, I'll put the app on openrepos. ;)

Has someone experienced (and fixed) something similar?

Re: Jolla Tablet LCD error
 

Me! I have experienced similar. I don't know why(I was trying Glacier?) but my tablet got to boot loop last summer. Or it just tired to boot with Jolla+Intel logo on screen, didn't start or didn't shut down. I didn't notice that Jolla+Intel logo screen was stuck there and I went to sleep.

Next day I flashed tablet with that leaked flasher+SFOS image and noticed same issues as you. Screen was flickering and Jolla+Intel logo was 'burn' there. I was worried but after 5-7 days with slight usage(couple hours) everything was back to normal. :)

Re: Jolla Tablet LCD error
 

It happens sometimes for tablet. Just leave it turned on for some days, it will gone itself :)

Re: Jolla Tablet LCD error
 

Was wondering if this is a moisture condensation problem?

Re: Jolla Tablet LCD error
 

Thanks guys!
I'd say the burn in is mostly gone.

Did you encounter the flickering as well or is that unrelated? Because that's still not nice to look at. But at least it's good enough for me to test i486 builds again without getting angry in an instant.

Either way, I think I'll put the (reeeeallly simple) app on openrepos after adding a small seizure warning tomorrow – should do no harm and maybe even help someone.

Re: Jolla Tablet LCD error
 

yes images glitch with flickering.

Re: Jolla Tablet LCD error
 

Thanks again, all!
Now that I'm relieved and less stressed out I see that eekkelund mentioned it, as well. I somehow missed that before. :)

Re: Jolla Tablet LCD error
 

Any idea what's the root cause and physical phenomenon that this is based on?

From the description I understand that it is nothing like "burn-in" of old CRT's or plasma tubes which results from the same intensity of light being constantly exited off the luminence material which leads to physical wearing-out of the said material.

Also same kind of phenomenon might be possible on OLED displays where bright pixels are worn out, maybe via electomigration of the materials? However this also happens only when the same image is burned to the display for a long time...

But LCD's are a different thing, the colour change in pixels is achieved via polarization change of the material, and in these descriptions the image did not "burn-in" when the same image was shown for a long time but somehow instantly when the device rebooted spontaniously?
And is it so that the image was visible also when the device was turned off?

Re: Jolla Tablet LCD error
 

I at least thought so, but it was hard to tell for sure. You're right, burn in as such can not happen. I haven't got an Idea what the cause could be. My first instinct was that the display might need some kind of "shut down" impulse/command to correctly "clear" the stuck liquid crystal matrix, but… well… that has to be rubbish, as well, or colour e-paper would have been much easier to develop. Also, switching it off and on again would've helped. ;)

I found some time to publish the app to openrepos – let's hope no one needs to use it. Or that it at least helps a bit if someone does.
And yes, the icon is supposed to be this ugly, because the app is, as well. :cool:

Re: Jolla Tablet LCD error
 

I am only speculating, but a long time ago as a young electronics hobbyist I was playing with LCDs taken out of calculators and digital watches and very quickly discovered a disturbing fact. That polarization change is achieved by applying a voltage between two transparent electrodes with the liquid crystal between them. BUT - any segment thus activated remained dark for only a split second before it started fading back to transparent, even though the voltage was still applied. I had to reverse the voltage to activate the segment again. Even worse, leaving the voltage with the same polarity applied for a long time could damage the segment permanently. "A long time" meant something like a few seconds. In short, for a proper operation of an LCD, you need to feed the segments voltage with quickly alternating polarity, in the range of at least a few Hz. Dedicated LCD controllers do this. My understanding is that some electrochemical processes start happening in the crystal if you don't.

It is possible that the forced power-off disrupted this alternating current mechanism and left the pixels activated for longer than their healthy dose with the same polarity voltage. By the sound of it, the damage was not permanent but possibly long lasting.

Re: Jolla Tablet LCD error
 

Thank you @pichlo, your explanation might be correct!

I am aware of the 1st fact you describe, I too played with watch LCD displays and batteries when I was a kid and remember that the number segments only blackened for a moment when DC voltage was applied over the electrodes.

However I never came across the 2nd phenomenon that you describe, that there was permanent change in the display when the charge was left on longer. That indeed seems to be what's happening here.

Re: Jolla Tablet LCD error
 

for me it looks like video memory/framebuffer corruprion

Re: Jolla Tablet LCD error
 

Might look so, but then it would be cleared when the device is switched to POWER-OFF, hmm?

Re: Jolla Tablet LCD error
 

well, probably, but mobile devices are powered always and who knows maybe video ram is also powered somehow while switched off :)

Re: Jolla Tablet LCD error
 

That's the thought I had when I tried to drain the power as much as possible – perhaps I just wasn't able to do drain it enough.

Quick update:
I've noticed the device is now freezing more often than before. Thrice in the last 24 hours, mostly when idling with display on, showing display glitches. But this could be random, as well. After rebooting swiftly, there are no new visible artifacts.