Lcd Flat Screen Trouble

[meadish_sweetball]

Hi,

Any ideas what may be the cause of the flickering pixels in dark areas I get occasionally? It seems the problem is with the external LCD monitor (Samsung SyncMaster 191T, bought 1 year ago), because the internal LCD screen of my laptop looks ok.

Symptoms: The dark areas, of for example the smilie, as well as the mouth of the smilie have green flickering pixels in them, and normal black text is also not as crisp and sharp as before.

Is this a backlight problem or something else. Is there anything I can do about it?

Cheers for your time in advance.

/Meadish

[Firefoxx]

A backlight problem will affect all pixels, not only the dark ones. It sounds more like a signal problem. You can try connecting your laptop to another monitor to see if the problem lies with the laptop or the monitor. What refresh rate do you have it set to?

[meadish_sweetball]

Is that the Hz? Hang on, will check.

It's set to 60 Hz, and it's been on that setting since I bought the monitor one year ago.

This current problem is not new, I have had it before, but it has resolved itself spontaneously without me being able to pinpoint the problem.

Somebody suggested it might be that one or more of the the male cable connector pins are pushed in, causing the signal to become distorted or unclear, so I checked both connectors... but they seem ok. I also switched the connectors, connecting the monitor side connector to the computer side connector and vice versa, and then restarted the computer, but that did not change anything. I have tried to wiggle the connectors on both sides too to see if this changes anything, but it doesn't look like it does.

If it is the cable, how much is a new VGA cable these days? If cheap enough it might be worth buying one and testing.

[Firefoxx]

VGA cable is in the 100-200 baht range, approx.

60Hz is correct, the recommended setting for LCD displays (not CRTs).

You could try connecting the LCD to another computer. Basically pinpoint where the problem is originating. If it's a faulty connection, it shouldn't resolve itself. It sound like it might be bad joints somewhere, perhaps in the connectors or in the solder job.

[autonomous_unit]

Did it resolve itself while you were checking connectors? After a year, it could have been corrosion forming on the connectors which was then scraped away (at least partially) by your physically reinserting them. At video frequencies, all sorts of messy crosstalk and noise can happen over bad connections.

Is the connection VGA (analog) or DVI (digital)? I'd expect flickering in dark pixels to happen with a noisy analog connection. A bad digital connection would be more dramatic distortion or failure and not related in the same way to pixel color.

[meadish_sweetball]

VGA. And it still hasnt resolved itself, unfortunately.

[meadish_sweetball]

Picking up this subject again since the problem has reappeared (it did however resolve itself spontaneously last time).

I have tried all the things I did last time with no results. Used W 60 on the connectors and cleaned them.

Also tried the DVI out, but with DVI, the exact same problem appears when connected to my stationary computer. The warranty is not valid anymore, but I am considering taking it to the store anyway to see if they can fix it and if so, how much they would charge.

Anyone got any ideas?

Cheers

[Tywais]

If you know how to, remove the video card from the slot and clean the connector edges lightly with a pencil error (not ink eraser) and wipe with a piece of paper when done. Re-install the card and be sure it is well seated and try again. The fact it is effected from both VGA and DVi suggests either the card or the monitor. If your cable screws into the monitor (rather then a fixed cable) remove it and clean also and securely re-attach it.

[meadish_sweetball]

Thanks for the suggestions tywais. The thing is, two different computers give the same symptoms.

I usually have the LCD display as an external monitor connected to my laptop. The picture on the regular laptop screen is fine even when the green lines/dots flicker on the LCD display.

When I used the DVI cable, I connected it to a different machine, a stationary computer - and got the same green flickering dots and lines in dark areas. The picture on the regular monitor of this stationary machine is also fine.

So since both the DVI cable and the VGA cable, connected to two different machines, give the same symptoms, I guess I can be fairly certain the SyncMaster LCD is the problem, and not the connectors/cables? Not 100% though I guess...

Also, not sure how to remove the video card from the laptop, I havent dared to go very far into it since there is so little space.

[Tywais]

Thanks for the suggestions tywais. The thing is, two different computers give the same symptoms.

Sorry, should have read your OP a bit closer. The university network is having some severe latency problems at the moment and hard to get a screen up. You are right, two computers - two cables, leaves it to the monitor. Possibly the monitor connector itself, unless you have two connectors on the monitor, DVI & VGA like mine. Could be just a loose connection inside the monitor. Ok, I know I'm going to get jumped on for this, but tap the top and sides of the monitor and see if it effects the image. (old technology trouble shooting techique).

[meadish_sweetball]

Cheers again - tried it -fairly hard too ... no change though.

The LCD display has separate ports for DVI and VGA just like yours.

Also tried changing the power cable, but that didnt do anything either.

[meadish_sweetball]

I finally smacked it REALLY HARD... and it looked normal for 30 seconds before reverting to the flickering (to a worse state than before too, I think ).

So that would confirm the issue is a bad connection somewhere inside the actual display, I guess.

EDIT: Smacked it again and now it's been normal for all of 10 minutes.

I guess it is a masochist, should have noticed earlier and bought it a leather outfit.

[elkangorito]

It is also worthwhile to note that LCD screens have an expected 'pixel failure' percentage. Some more expensive screens indicate that the monitor may have a certain pixel failure rate. If this rate is exceeded, the manufacturer will replace it or fix it under warranty. The cheaper models will have no warranty for any level of pixel failure.