I actually fully disassembled one of them looking for exactly that. I adjusted my DSlite using the ones right next to the battery so I know what you're talking about. While I'm not incredibly knowledgable about hardware, I certainly didn't see anything like it that indicated it was adjustable.
And that's kind of what I'm wondering now: Would a theoretical mod be possible if you were to intercept the voltage to the screens and add your own potentiometer? I imagine such a mod would be incredibly difficult if it's even possible, but maybe someone with some electrical background might be able to imagine a solution
As far as I can tell, all of the IPS panels are affected and none of the TN panels are affected. I've noticed some variation in the IPS but given the quantity I've tried out, I'm reluctant to believe there exists an IPS panel without the problem to some extent
Yeah the GBA had the adjustment behind the back label (remember back in 2001-02 when everyone thought this was adjusting brightness?) and the DSi and DSiXL had it behind the battery cover; two different potentiometers for the two different screens.
Why the new3DS doesn't have the adjuster when clearly they are using the same multiplexing-type screens is beyond me. My guess is there is one somewhere but it's not adjustable by using a screwdriver. Maybe a value set by a SMD resistor? Or maybe it's even set in software or programming?
While someone figuring it out or some mod would be awesome, I doubt enough people notice it to be bothered by it. This thread was the only thing I could find regarding complaints, and it seems like the only people here who notice it (myself included) are the types who notice things like motion blur, rainbowing on certain projectors, etc.
What's funny is I noticed my top new3DS screen has a yellow tint to it but it doesn't bother me much. The "scanline effect" (multiplexing) on the other hand is driving me nuts. I think the only way to "fix"it is by continuously returning them until you find one that was calibrated properly "by accident".
I wonder if Target is going to ban me from returning for repeated returns? I know Best Buy does that. I know it's a bid obsessive but it actually makes me unable to enjoy my new3DS.
A small sidenote which I think is kind of interesting but I had two 3DS XLs (not the new one) and the original 3DS and neither had this issue, which is weird, because every other Nintendo handheld since the GBA (maybe even the GBC, I don't remember) has had this issue. Maybe I just got lucky with my original 3DS systems? But the problem is there on all of the new3DS's, clear as day.
Another easy way to spot it is in Super Mario Bros 2 (either from the E-Shop or the SNES emulator on the DStwo running Super Mario All Stars then SMB2US), go through the first door in the first stage and I notice it very easily on the blue sky. If you gently move the console you'll see the multiplexing lines everywhere. The top screen is not getting the proper voltage for some reason.
Even stranger is I have not yet seen this take place on the bottom screen on any of the new3DS systems. My guess is Nintendo is feeding identical voltage to both the top and bottom screens, even though they probably require slightly different voltage (the bottom screen has a digitizer, and the top screen is larger and IPS). I don't think the top screen being IPS has anything to do with it since every other Nintendo handheld exhibited this issue for me as well (besides the old3DS but maybe that was just luck).
I definitely know this is something that can be solved by multiple returns and looking for one that's perfect because on all 3 new3DS systems I had, the problem was way less noticeable on one than the other two.
One weird sidenote as well is that my DSiXL had the same issue, and I was able to fix it with a minor pot adjustment, however it keeps coming back after a few days. Really weird. I even used hot glue on the potentiometer so I can definitely rule out that it was moving on its own or something.
Nintendo's quality control as of late has been really horrendous. Remember the original 3DS scratching the top screen when you closed it? And 3DS XL systems with dust under the screen right out of the box? The volume slider on one of the new3DS's that I got is about 20 times harder to push up and down when compared to the 3D slider. The other two didn't have that problem. Factory workers tightening the screws too hard? No idea.
I hope there's a fix for this, but if not, I will keep seeking out a perfect unit. Now I'm just worried about what the OP said about some of the systems having a worse "head tracking" capability than others!