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AOC AG251FG issues

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AOC AG251FG issues

Postby Annigo » 13 Oct 2018, 19:38

Hello,

I bought AOC AG251FG (240Hz, G-Sync) monitor and I am experiencing following issue:
phpBB [video]

More samples here: https://imgur.com/a/GoWKeWr
All captured with a phone at crappy angles, I know.

This looks like some kind of signal noise to me, but I'll leave it to You.
This happens mostly in the right part of the screen as shown, but often there's also a thin horizontal line somewhere near the bottom as well. Unsure what conditions needs to be met for this to happen - although it looks a bit random, I noticed it happening more frequently in presumably low FPS moments, like score board or loading. This includes Windows 10' welcome screen, when user profile is loading.

Rarely there's also part of the screen displayed in different place:
Image

Is this something known and can be done with, or this unit is simply damaged and should be returned / replaced?

Here's some background information:
  • Tested on both new PC (Win10, GTX 1080 Ti, latest drivers) and previous PC (Win7, GTX 970, few months old drivers)
  • Used DisplayPort cable included with the monitor. For test tried replacing the cable with other DP - ended up with blank screen. However, local shops ran out of DP cables, so I got random one, uncertain what version of the cable - might not suit the needs, therefore may be irrelevant.
  • 240Hz setting in Windows, G-Sync enabled for both windowed and fullscreen.
  • In monitor OSD: Overdrive set to light, Shadow Control set to 0.

Please ask if there's something more I can test or provide. Thanks!
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Re: AOC AG251FG issues

Postby RealNC » 13 Oct 2018, 19:48

Looks like damage to me. I recommend RMA.
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Re: AOC AG251FG issues

Postby Annigo » 30 Oct 2018, 15:53

I haven't found anything more on this topic, so I returned it last week. Here's newer sample to better show the issue:
phpBB [video]

By the end you can see it doesn't happen anymore - as if some conditions had to be met. While I am uncertain what condition it is, I noticed it happening significantly more in certain situations. On top of it, it always happens in Overwatch after the match, after stats has been displayed, just before screen turns black:
phpBB [video]



Yesterday I found following video, where someone has the same problem (but in middle of the screen) in other monitor using the same panel: https://www.youtube.com/watch?v=3oci3XJcMU8


Hopefully better luck next time.
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Re: AOC AG251FG issues

Postby RealNC » 31 Oct 2018, 10:24

Wait, you returned it, got a new one, and it still has the issue?
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Re: AOC AG251FG issues

Postby Chief Blur Buster » 31 Oct 2018, 14:34

Vertical glitches like that is often something going on in the monitor instead of the computer -- basically glitching occuring related to the LVDS ribbon cables to the LCD panel glass between the TCON (timing controller that refreshes LCD pixels) and the screen glass.

Often the widths of the glitches are approximately 1/8th screen width or 1/4th screen width, and it looks like the rightmost band is being effected, and the horizontal spaces between the ghost images is also similar spacing. So your two glitches are related since that's the segmentation of the refreshing system becoming visible -- modern LCDs are often subdivided into vertical strips independently refreshed by separate ribbon cables in perfect sync. If one glitches, that creates band widths or horizontal-shifts (e.g. duplicate vertical columns or ghosts) equivalent to 1/4th screen width (4 channels) or 1/8th screen width (8 channels). That's a dead giveaway of a glitch inside the monitor, not inside the computer.

But two different samples? I now have a theory;

Longshot (10% chance) is an RFI/magnetic interference of a poorly shielded monitor.

Could you do a test -- and relocate the monitor further away from electronics, transformers & gadgets?
-- Move routers very far away from the monitor
-- Move computer another foot away from the monitor
-- Move all transformer boxes off the desk
-- Move all power bars off the desk (if any sitting on desk under monitor or behind monitor)
-- Move monitors further away from the wall at the back (e.g. power wires hidden in wall behind monitor)
-- Move all antennas further away from the monitor (TVs, radios, routers, phones, etc)

In simple terms when testing for interference-related issues.... Put at least 2 feet of "no-electricals" space in front, behind, left, right, below, and above the monitor that contains NO wires, NO electronics, NO gadgets, NO wires-for-other-things. The only wires should be the video cable and the power cable. And maybe your wired keyboard/mouse. And any antennas, move as much of them to opposite side of room (e.g. routers).

Test that. Let me know if the glitching reduces or disappears.

I've seen radiofrequency-interference (RFI) glitching in monitors before. The most famous case is the LG 5K monitor glitching with a nearby router ("Keep your monitor at least seven feet away from your router"), but I've seen glitching in a GSYNC monitor caused by a poorly-shielded big-ass 200-watt power brick sitting UNDER the monitor. It's amazing how magnetic fields can inject glitches into nearby cheaply-shielded electronics.

Also get a ground-fault tester (under $20) -- a bad ground can also cause lots of glitching in a computer system that is hard to trace. Those are cheap at Home Depot, Amazon, and eBay. Wiring faults in home wiring can generate massive noise that sometimes wreaks havoc in electronics in weird ways -- whether strange static in a speaker or glitching in a display or sudden surge of BSODs, etc. Missing ground, crossed wires, etc.

It may still be coincidental defects, or firmware bug, but seeing this happen to two samples is quite unusual.

So it's prudent to at least quickly rule-out possible interference issues.
Rare as they are, they happened often enough to others for me to warn about this...
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Re: AOC AG251FG issues

Postby Annigo » 01 Nov 2018, 10:36

RealNC wrote:Wait, you returned it, got a new one, and it still has the issue?

No. The newer (video) samples were recorded after posting the forum thread, before I eventually returned the monitor, so it was the same monitor unit all along. Now I am reconsidering monitor choice. Sorry if I worded last post poorly.


Chief Blur Buster wrote:Could you do a test -- and relocate the monitor further away from electronics, transformers & gadgets?

I don't have it anymore, so I cannot test. As mentioned just above - it was the same unit all along, sorry for misleading. However, I can describe how it was set up:
The PC stands on floor, next to the desk, about 1 meter horizontally and 0.5m vertically away from the monitor. There were no other electronics other than that, excluding keyboard and mouse about 0.6m away, whose wires go under the desk (about 0.2m from monitor). The wall behind has no power wires at this height, so shouldn't be an issue either. In any case, that's significantly over 2 feet (~0.6m). Router is in another room, up to 5 meters far away.
In the other thread I mentioned having 2 IPS monitors - I tested the AOC in all 3 scenarios: with them turned on, completely plugged off and even without them being on the desk at all. Also tried plugging the monitor's power to different contact. I also mentioned using 2 completely different PCs with other version of operating system and graphic card drivers, so I doubt both generate same "noise". Old PC has 550W power supply, and the new one 750W (be quiet! Straight Power 11 750W (BN283)) if that matters.
I don't know if any setup changes affected the glitches intensity, because at that time I found them more random. I found consistency in some situations, and always in OverWatch in score screen, just before the screen turns black to load next map, as shown above.
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Re: AOC AG251FG issues

Postby Chief Blur Buster » 01 Nov 2018, 19:30

My recommendations mainly pertains to getting the exact same LVDS glitches (vertical band glitching, 1/4 and 1/8 screenwidth) on multiple monitors. In that situation, it can sometimes be too coincidential -- and interference needs to be ruled out.

However, if it is only 1 monitor -- disregard my suggestion and do a simple RMA. These LVDS-type glitching are usually cleared up after 1 monitor exchange. If a monitor is out of warranty, a loose LVDS cable connector can be jiggled to see if this type of defect disappears.
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       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors
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