Hello!

I have a problem with my laptop Dell Inspiron 3593 (with InnoLux N156HGA-EAB built-in screen). It gives me eyestrain (dry eyes feeling) within a few minutes when I start using it. I can see that the screen is pulsating slightly (it's almost invisible). It doesn't matter whether I use it in daylight, artifical light, both of them or in darkness. Also whether it's connected to AC or not.
It happened since I unboxed it. First it was completely unusable, giving me more eyestrain, headache and nausea. I tried changing it's settings, but it didn't work.
After a few months I got a job which requires using it, so I didn't have time to send it to warranty repair (and they may claim that they don't see any problem), so I decided to modify the hardware myself. I soldered an electrolytic capacitor in parallel with backlight LEDs - it helped a lot, but it's still worse than a standard laptop screen. I thought, maybe that capacitor isn't enough to stabilize LEDs current? I tried to add an inductor in series with LEDs, but I broke something (it requires precise soldering and avoiding short circuits) and backlight went out. I found a temporary solution - bought a small regulated inverter module, soldered it's input to USB plug and it's output to LEDs (with capacitor and inductor forming LC filter). I feel it's similar or slightly better quality to previous solution (when I soldered a capacitor to LEDs powered by original inverter).

However, there must be some flickering coming also from LCD. I tried different solutions, but it didn't help, i.e.:
-changing screen frequency and definition (current is 60 Hz, 1920x1080)
-changing /etc/default/grub: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.modeset=0 i915.enable_dc=0 i915.enable_rc6=0 i915.enable_fbc=0 i915.panel_use_ssc=0 i915.alpha_support=0 i915.enable_ips=0 i915.enable_dpcd_backlight=0" (this is how it currently looks like - previously I tried also GRUB_CMDLINE_LINUX_DEFAULT="quiet splash
i915.enable_psr=0", but it also didn't help)
-changing desktop to KDE (it installed KDE Plasma)
If I remind something else what I tried, I will write.

About my experience with other devices
Previously I had Asus X55VD laptop with preinstalled Windows. On Windows it worked rather good. Except that in the evening I got a little eyestrain from backlight PWM, but only after a few hours of using, not a few minutes. On Ubuntu it was unusable (similar to Dell Inspiron 3593 before that hardware modification), on other Linux distros too, only Mint was slightly better. When fast scrolling some document on Ubuntu, I could see diagonal tearing.
Other computers (laptops and desktops) don't cause such problems for me - I used many different of them, with Windows or Linux.
Last year I bought Elitecho smart LED bulb - it caused the same symptoms (especially dry eyes) when dimmed or with mixed color temperature (it has sets of warm and cool white LEDs which can be dimmed independently). Here I also soldered some capacitors - and it also helped much, but not enough.

Could you please help me with my Dell? What should I modify in settings/software? And what screen would you recommend for replacement (with properly powered backlight and correct LCD panel, if it also matters)?

That's really interesting 🙂

Something that may interest you, is that the voltage applied to each individual pixel on a LCD to control the colour inverts every frame. If you apply a dc current to a liquid crystal it degrades, so by inverting the voltage every frame they last longer. If the inversion is not well configured (for reasons I don't know) you'll get a flicker at half the frame rate of the monitor as pixels brighten and dim with each inversion. This is totally independent of the backlight. It does mean you can never truly get a flicker free LCD monitor, however perfect you get the backlight.

18 days later

I booted Hiren's Boot "CD" (actually pendrive) to try something Windows-based. I also started feeling dry eyes and noticed that display seems to flicker, although I haven't booted Linux before it this day. However, it couldn't connect to Internet, so I'm not sure if it managed to load proper drivers for this device. First I tried default screen settings (I don't know what they were), then I chose 1920x1080(32B/60Hz) and 1024x768(32B/85Hz).
I have a DSO150 oscilloscope and I'm trying to measure light pulsation with it, so maybe it will lead to conclusion what causes it. Do you know some circuit to do this? First I tried connecting a solar cell from a broken calculator with some resistor in parallel. However, when the resistance was too low, the voltage was also low, but when I increased it, mains hum covered the signal. And I read that solar cells react quite slowly for light intensity changes because they have large area and thus large capacitance.
Next I tried a red LED in a clear bulb as a light sensor instead of the solar cell (for those who don't know, LEDs can also work in a reverse way, generating voltage from light). There was also a weak signal, too weak to detect any pulsation because of the mains hum. So I tried some amplifier (photo below, first I tried with 10K resistor, then I added 1K in parallel to it). When the LED is illuminated by a flashlight close to it, there's almost 9V on the output, but laptop's screen isn't bright enough to get any signal. Do you know how should I modify it?

    TheRollingBones

    I made a detector out of one of these soldered to an audio plug. Works well enough to detect flickering in lights, kind of works for screens but not very well.

    a month later

    I bought a new panel AUO B156HAN06.3. It has DC powered backlight, so I don't have to use that external inverter powered from USB. It's better than out of the box laptop, but there's still some LCD flicker. How can I fix it, the best without installing Windows?

    3 months later

    I bought Windows 10 and installed it, updated and installed graphics driver from Dell site. However, I can still feel some eyestrain quickly (while it doesn't occur when I'm using i.e. other laptops or smartphone).

    TheRollingBones We have our oscilloscope thread, which discusses solutions to make light flicker visible. Maybe it helps you, and perhaps with your electronic knowledge you could even help improve it? To make the detection truly sensitive we'd need to construct a transimpedance amplifier circuit, and one that won't affect the bandwidth negatively. No one has done that yet. But the current solution should detect strong flicker at least (I was able to detect 10 MHz on/off PWM).
    https://ledstrain.org/d/312-homemade-oscilloscope-to-detect-pwm-diy-guide/42

    dev