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felipe_s

17 Posts

156629

August 6th, 2006 18:00

2007 WFP (A02) Flickering!

Hi,

I bought a 2007WFP monitor recently and I really like it, BUT it "flickers", just like a CRT on 60Hz refresh rate. I decided to make this a seperate posting, since the problem has been mentioned before please move my thread if you feel this is inappropriate.


The flickering is only visible in some specific (midtone) areas, e.g. 50% gray, and very bright or dark areas are generally not affected if my eyes can be trusted.

I'm using the monitor with an Ibook G4 800Mhz (32MB Radeon 9200) via the VGA adapter, and at first I thought the flickering could be caused by the bad/weak signal quality - although a friend's Dell 21" TFT worked fine some months ago, so I defibrilated my old PC (AMD 1700+, Win2k SP4, 512MB RAM) again to see if this could indeed be the cause of the problem.

I tried a Radeon 8500 128MB (VGA and DVI), a Matrox G550 (VGA and DVI) and the internal Geforce 4 MX (VGA), but the flickering is still there, even with the PC.

The monitor is calibrated with a Gretag EyeOne since I'm using it for graphic design, but it doesn't matter which profile I use, flickering is still the same.

I'll call support again on monday to see if they know anything, but do you have any input on this?!


--

And since we're talking about the 2007WFP, some minor observations:

The Bad:
- I had to return the first one since it ran so hot I could barely touch the top area.
- Both my current (A02 made in China) and the faulty one (A02 made in the Czech Republic) have the flickering.
- Both still suffer from VERY faint gradient banding, even when properly calibrated.
- The gamut is good overall, but the blacks are clipped quite severely (for a TFT), and very noticeably so compared to a 23" Apple Cinema Display.
- The "contrast" setting is not available" via DVI, which is quite annoying if you plan on calibrating the monitor.

The good:
- No discolorations, casts, darkening etc. whatsoever, VERY homogenic display, I hope it stays that way (unlike the Apple Cinema Displays)

Cheers,
Phil

Crazy_Eddy

7 Posts

December 27th, 2007 11:00

Just curious, has anyone tried a dual-link DVI-D cable with the 2007wfp to see if it helps with the flickering?

Somnio

180 Posts

January 3rd, 2008 13:00

Just to clarify, we're talking about two different issues here.

  • First you have a color flickering, due to color modulation or FRC on VGA mode, visible mostly on some websites that have a specific tile pattern. Can be minimized using the OSD- Display Settings- Phase setting or switching to DVI input.

  • The other case is actual backlight flickering, visible on white backgrounds. This one is related to poor modulation of the backlight, and not related to the video input or display settings. It is confirmed that some monitors are worse than other on this, and the only way I've found to get rid of it is raising a bit the brightness value.

Crazy_Eddy

7 Posts

January 3rd, 2008 17:00

Definitely not the tile pattern that i have issues with, since I notice it with solid colors like blue, grey etc. I thought the tile pattern flickering might have something to do with inversion patterns? FRC etc is not supposed to happen on native 8-bit panels like S-IPS right?
 
I use DVI anyway. I recall reading somewhere about the Genesis controller used in displays being rather sensitive to the video signal quality, and how dual-link DVI cables enable the use of two TMDS transmitters for a 'stronger' signal. Forgive me if its not correct, since I have no clue about such stuff.. just desperately looking for solutions :)
 
You are right though.. increasing brightness does reduce the flicker - BUT it becomes too bright to look at for too long. Backlight modulation should be a simple re-design, why doesn't Dell get on it? I really love the monitor apart from the flickering!

Somnio

180 Posts

January 3rd, 2008 19:00

@Crazy_Eddy: yep, that is the backlight effect I'm talking about. Its something particular on each unit, because I never noticed it on mi previous 2007wfp A02 after a year and half of constant use at 25% brightness. Indeed can be described as "like a CRT working at 60hz".

About what you say about DVI signal seems odd, because I thought that a digital signal can not be degraded (is there or not is there). In my case, I have exactly the same configuration used on my previous unit BUT I replaced the DVI cable, so I will check it, just in case.

Somnio

180 Posts

January 7th, 2008 17:00

BTW: I left here a gray background on where the effect is most noticeable, just for check and compare issues (*).



(*) Tested on a 2007WFP A04 S-IPS / DVI input / ATI Radeon 9800 / 25% brightness / desktop mode

Message Edited by Somnio on 01-07-2008 01:48 PM

Crazy_Eddy

7 Posts

January 7th, 2008 21:00

^ Yep this shade of grey makes the flickering most noticeable (for me, the classic windows theme with the blue desktop background also produces a very noticeable flicker). I also notice this weird web-like pattern across the screen when photographed with a digi cam - is it normal? (click the pic for the larger version) :
Free Image Hosting at www.ImageShack.us
 
You have a valid point about the digital signal over a DVI cable either being there or not! I had read this post and assumed it might be a DVI cable issue : http://www.bleedinedge.com/forum/showpost.php?p=103573&postcount=9 . Single-link DVI cables with the 2007WFP are a cost cutting move, since a friend with a 2005WFP mentioned that he got a dual-link DVI cable with his screen.
 
BTW it might be interesting to note that Xbit labs found an anomaly with the Dell E207WFP backlight modulation producing a 60Hz 'flicker' : http://www.xbitlabs.com/articles/other/display/20inch-5_12.html . Could very well be the same issue that's plaguing the Dell 2007WFP.
 
I'm not sure if I mentioned this earlier, but changing to portrait mode makes the flickering on the 'Rizon drum n bass' website vanish for me. The flicker with solid colors can still be seen though.
 
Anyway, I've decided to return my 2007WFP panel since I can't find any fix for it and even when I don't 'notice' the flicker, the eventual eye strain makes it obvious. Sadly where I live, I have no other quality panel options but a flood of TN based screens. Does anyone know if the 2007FP has the same flickering issue? If not, I might try my luck with that panel (apart from the discomforting fact that it uses the less superior S-PVA panel).
 
-----------------
 
To anyone from Dell reading this post : There IS an issue with the panel and it does look very much to be with the backlight modulation - all this info has been very well researched by the community and put out to help you guys work on a solution. A fix from your end would have ended the search for a good 20" panel for me and many others. I will reiterate - the panel is excellent for the price apart from the flickering issue. It's just saddening to see you people cover up and claim its not an issue.
Message Edited by Crazy_Eddy on 01-08-2008 04:34 AM

Message Edited by Crazy_Eddy on 01-08-2008 04:42 AM

Message Edited by Crazy_Eddy on 01-08-2008 04:46 AM

Somnio

180 Posts

January 8th, 2008 09:00

@crazy_Eddy wrote:
^ Yep this shade of grey makes the flickering most noticeable (for me, the classic windows theme with the blue desktop background also produces a very noticeable flicker). I also notice this weird web-like pattern across the screen when photographed with a digi cam - is it normal?

Yep, its the lens of the camera that "sees" the pattern of LCD cells, and slightly deforms its.

@crazy_Eddy wrote:
Single-link DVI cables with the 2007WFP are a cost cutting move, since a friend with a 2005WFP mentioned that he got a dual-link DVI cable with his screen.

Thats a good point. My actual DVI cable is single-link, and I can't remember about the old one that was returned to RMA along with the fault panel. Anyway, the effect mentioned in the post is more like a total switch off of the screen than an actual hight speed flicker.
The X-Bits labs review seems to be exactly the effect that we currently see on our models, and I really like to hear Dell opinion on this, because seems to me that the problem is more and more related to a bad quality electronic inside the panel.

I'm not giving up anyway. Since the problem can be now related to the electronic and not the backlight itself, I'm suspect about the genesis chip. I know that this chip is pretty sensible to the DVI output of the video card, and if its not getting a perfect digital signal from the computer, several effects like sparks and banding can be seen on the screen.

Currrently I'm playing a bit with the DVI options on the video card: "Alternate Operational Mode" and "Reduce DVI frequency" to see if something changes. I'm trying NOT to seek for the effect, so, this might take time :P Also, I have a shielded VGA cable ready to test on this computer and a notebook.

PD: If anyone can try using a dual-link cable, just to confirm that is not related...

EDIT: interesting thread on Apple Support Forum:
http://discussions.apple.com/thread.jspa?threadID=1045078&tstart=0

Message Edited by Somnio on 01-08-2008 01:51 PM

Somnio

180 Posts

January 10th, 2008 13:00

So far, moving out any electric device and plug the display directly to the wall proved to do nothing. Also, I've played a bit using the DVI settings on my video card without any strong result. Its picky to get, sometimes the flickering is there, sometimes don't.

@Crazy_Eddy: I'm now using the VGA input and seems to behave a bit better, but can't tell because the bright settings are a bit different too. Can you please check your unit on VGA mode?
EDIT: nevermind... flickers :(

Next: If vga fails I will try on another computer. Also, I've downloaded SOFT MCCS to try reduce the DVI mhz to 50 or so...

Message Edited by Somnio on 01-10-2008 09:34 AM

Crazy_Eddy

7 Posts

January 11th, 2008 11:00

Well I found a pseudo-fix for the flickering.
Since it is indeed related to the backlight modulation in the panel, I just turned up the brightness to 100% on the panel. I have an nVidia card, so went into the nVidia control panel and reduced the (software?) brightness there to bring down the overall brightness again to reasonable levels. I can't notice any flicker anymore! (and neither is it over bright)
 
However the downside is that the contrast, gamma, etc etc need a lot of tweaking to get it right and unfortunately I dont have an LCD calibrator unit with me.
For example, dark areas look completely dark (not able to distinguish between black and lighter shades of black) and vice versa with the bright areas. Reducing contrast does bring it back to balance, but then the colors look a little washed out.

Somnio

180 Posts

January 11th, 2008 13:00

Yep, that solution come to my mind, but IMO you loose a lot of gamma this way, and plus, the lifespam of the backlight will be short.

I'm still curious about the solution posted on the mac forum above. Some people managed to almost correct the pulsation just increasing or reducing the output of the DVI to anything different of 60hz. The software recomended there is only for mac, but perhaps we can archieve something similar using SOFT MCCS

I will love to hear something from Dell, about if the pulsation is related to bad regulation of the inverter or just some kind of out-of-sync condition between the display and the video card (as the above fix seems to suggest).

Somnio

180 Posts

January 14th, 2008 15:00

Tested using PowerStrip to override Windows driver and force some custom clock settings on the DVI input. None of them proved to be any useful. So, currently the only way to get rid of the flickering is to raise the brightness to 50% or above.

Crazy_Eddy

7 Posts

January 14th, 2008 20:00

^ Thanks a LOT for all the trouble you've been taking at finding some tweaks around this problem. Pity it didn't bear fruit, but your efforts are well appreciated! :)
 
I do notice some flickering even at 50% (the default), and the X-bit labs review said the flickering on the E207 disappeared above 60% brightness. Since I did not have the patience to try at 60%, I just did the logical thing i.e. taking it to 100% assuming any backlight modulation would be null.
 
Dell has approved my refund and are waiting for my word to go ahead.. however after finding this workaround, I'm in a bit of a dilemma over what to do! Please advise - is it possible to tweak and set up the monitor right even at this high brightness or am I better off with another monitor? Do note, the only other monitor options I have where I live are TN based screens (at half the cost!) or one or two rare S-PVA based ones.
I'm not too fussy about colors, though I still notice the washed out look on TN panels.. but to me better viewing angles are what I enjoy most on the S-IPS.

Somnio

180 Posts

January 15th, 2008 11:00

Its a shame that Dell has no information about this issue. I left a PM to ChrisM to see if he can drop us a line or two. If the issue is truly related to the backlight inverter, we are talking about a fault made by the panel manufacturer, that uses bad quality components. Several Cinema Displays and MacBook Pro got the same flickering problem, and since there is no way to know if the new panels got the issue corrected, we must assume that any display exchanged can have a similar behavior.

This video shows exactly what I saw when I plugged the 2007wfp A04 to a Dell Vostro 1500. Showing the same desktop image, Vostro's display -running on batteries, display dimmed to 25%- got a rock solid flickering free image, while the 2007wfp (25% brightness, 50% contrast) showed a visible flickering.

http://www.youtube.com/watch?v=20-NEgXUk5o

Said that, the only way to effectively correct the problem seems to be a repair, not exchange, but a replace of the logic board. Some Mac users actually managed to do that free of charge from Apple.

Another way is to change panel brand. S-IPS's are Philips/LG, I belive, so, getting a Samsung's S-PVA panel instead could be a solution. You can try exchanging to a 2407WFP or buying a new Samsung display.

Message Edited by Somnio on 01-15-2008 07:16 AM

Somnio

180 Posts

January 22nd, 2008 15:00

Waiting for the replacement (that I will make effective on a couple of months), I keep playing with the controls. I didn't notice before, but seems that since A03 the 2007wfp has a FRC or dithering layer that seek to improve the banding issue that sometimes can be found on A02 revision. Since the flickering is most visible on some color tones than others, perhaps can be related to a combination of a weak backlight and this new feature.

Anyone that want to try theory can do this:

- Enter the service menu holding down "menu" and "+" while powering up. Release and press "-".
- Select "soft dither" and swith it off.
- Exit the service menu, turn off and on again the display.

Remember: the "soft dither" option is only available on A03 and up revisión. Please, post any result here :)

For me, this *seems* to improve a bit the flickering. I still can see some kind of "motion" on plain gray backgrounds, but so far I can't notice a flicker without looking for it.

Message Edited by Somnio on 01-23-2008 05:03 AM

keldorr

29 Posts

January 23rd, 2008 14:00

Somnio, thanks for bringing this thread to my attention. As you know, I've got flickering with my 2007WFP Rev A04 (along with another issue).

When you turned off "soft dither" did that result in banding being an issue?

And with "soft dither" turned off, what brightness were you using while testing?

Finally, you said "Waiting for the replacement (that I will make effective on a couple of months)" ... what did you mean by that? That you've asked for a replacement from Dell and it will take a couple months to get to you? :O Or do you just mean that you're going to wait a couple months before you call for a replacement?

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