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LCD MONITOR PROBLEM


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22 replies to this topic

#1 preocupado

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Posted 10 February 2011 - 10:11 AM

Hi,

Ive been using a Princeton VL1916 19" screen for almost five years, and its screen image is now gradually appearing with outlines around areas with defined borders, like between a person and the background. Also, bars of streaks occasionally appear in the side corners of different windows, and rarely the whole screen changes color, but it has not gone black yet. This is getting worse all the time, and Ive noticed that it sometimes goes away when I give the monitor a slight shaking. Would you mind helping me diagnose the problem in order to attempt a home-fix, since I live in a rural area with no competent pc technicians.

Thank you.

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#2 Broni

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Posted 10 February 2011 - 09:08 PM

Same Problem in Safe Mode?

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#3 Platypus

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Posted 11 February 2011 - 06:10 AM

In my experience the most likely cause of an effect resembling your description is a poor contact in the LVDS (Low Voltage Digital Signalling) loom carrying signal to the LCD panel. Most monitor designs have this reasonably accessible when the monitor casing is opened. And usually it can be cured by cleaning and re-seating the cable connections. So if this is the cause, and you feel comfortable opening the casing (and you understand electrical safety precautions), then it could be curable.

To confirm absolutely that the cause is within the monitor itself rather than a computer video fault or a bad VGA cable, it would be best to arrange to substitute the monitor for the one on another computer, and make sure the problem still shows.

As per Broni's query, if the problem disappears if you start Windows in Safe Mode, that would also be a way of recognising the problem may be a driver fault. Although then you would not expect moving the monitor to change the symptom.

If you wish to try the LVDS repair and an illustration would help, I can probably organise some images.

Edited by Platypus, 18 February 2011 - 03:14 AM.

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#4 preocupado

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Posted 11 February 2011 - 01:28 PM

Hi Broni: Ill try safe mode and see what happens.

Hi Platypus: I certainly would like to try the LVDS repair and an illustration would definitely help. Thank you for offering.

#5 Platypus

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Posted 11 February 2011 - 09:25 PM

If you go ahead, observe electrical safety procedures, and consider static discharge (frequently touch the metal framework) to minimise the chance of "zapping" a sensitive component.

The LVDS cable is the white flat loom low in the picture of this monitor I currently have apart:

Posted Image

The accessible end can readily be unplugged and the contacts cleaned with a cotton tip moistened with alcohol:

Posted Image

Also included in the image is an example of alternative construction of loom. Securing tapes of foil are shielding against electrical interference being radiated (and black "cloth" ones can be too), and should be peeled back with as little damage to them as possible, and refitted similarly on reassembly.

The other end of the loom may be less accessible, on this monitor there's a small access hatch where the control loom goes, and you have to flip up a little latch bar:

Posted Image

Then as before the contacts can be cleaned:

Posted Image

It's harder to do anything with the contacts inside the sockets. You can obtain mildly abrasive contact cleaning strips, but for the plug type connectors, inserting and removing the connector several times usually wipes the socket contacts enough (then clean the plug contacts again). The flip release sockets do usually give enough access for a wipe with a cotton tip, be careful not to snag and drag a contact, or leave cotton threads behind.

Make sure everything is connected up again correctly before testing the monitor, although I've found LVDS connectors to be a bit touchy and sometimes need doing again to be right, so it's worth testing to make sure before completely reassembling the monitor.

Edited by Platypus, 18 February 2011 - 03:13 AM.

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#6 ThunderZ

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Posted 11 February 2011 - 09:33 PM

:thumbsup: Great tutorial Platypus.

One more thing if I may. I have found that the particular style of cables used in lap tops can become a bit brittle over time. Likely from heat. They can be very easy to break\tear across the tracers. Be extremely careful when dealing with them.

Do`t ask me how I know. :whistle:

#7 Platypus

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Posted 11 February 2011 - 09:46 PM

That's a good point. Things always need to be handled with due care, but the very thin flexible looms like the ones in laptops are less robust!

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#8 preocupado

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Posted 14 February 2011 - 12:54 PM

Hi

Thank you very much for taking the time to send me all this info. The reason for my delay in responding is because we are suddenly without an internet connection at home, and it has been hard for me to get to a LAN house at the local village (30 minutes from home by rutty, dirt roads) lately due to a heavy workload these days. As soon as I get all this work out the way,Ill send you some feedback and let you know what has happened. BTW, the monitor has not been giving me this trouble for the last few days, but Im sure it wont be long before it starts again.

Thank you once again

#9 preocupado

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Posted 17 February 2011 - 04:49 PM

Hi,

I had to wait for the monitor to act up again before being able to do the preliminary tests. Running in safe mode gave me the same strange patterns on the screen, but switching monitors gave me a perfect image, so it appears to be in the monitor itself. In this case, should I now try the LVDS repair?

#10 Platypus

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Posted 18 February 2011 - 03:11 AM

If you're using the same VGA signal cable when you get the perfect image on the substitute monitor, that would seem to prove conclusively that the problem is in the Princeton. If you can link to a camera shot of the screen displaying the fault, I could see if it looks like typical LVDS faults I've seen. But yes, really the only way to prove if it is bad LVDS contacts is to clean them up and see what happens.

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#11 preocupado

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Posted 18 February 2011 - 06:21 PM

Hi Platypus,

There was no way to test with the same cable since each monitors cable is permanently set into its respective monitor.

Also, please pardon my ignorance, but Im not sure how to do a screen shot.

#12 Platypus

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Posted 18 February 2011 - 07:33 PM

No problem, captive cables simply mean that the cable itself is one possible source of the fault, where the cable is removable it makes it easy to eliminate it as a cause just by trying another one. If cleaning the LVDS connectors made no difference, the VGA cable would be another thing to try, but not so easy to find a replacement. If it is the cable causing the problem, you'd probably find you could make the fault come and go, or change, by flexing or pulling on sections of the cable.

For the picture, what's generally called a screen shot is an image taken within the computer from the video card, and won't show how a monitor fault looks. You'd need to take a photo of the monitor screen using a phone (usually looks pretty blurry) or a digital camera. Then upload the image to a suitable hosting site and link to it with the Insert image icon on the toolbar above the text entry area when posting, or paste the image link provided by the hosting site into your post.

There is a screenshot tutorial here:

http://www.bleepingcomputer.com/tutorials/how-to-take-and-share-a-screen-shot-in-windows/

To use a camera image instead, disregard the first section describing getting a screenshot, and go from "Uploading the screen shot to an image site", but use the camera image. An image from a digital camera is usually rather large, and it's worth reducing the size using a utility like Irfanview, link in the tutorial if you don't already have it.

If it seems too involved, or you don't have the wherewithal to do it conveniently, it doesn't matter.

Edited by Platypus, 18 February 2011 - 07:34 PM.

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#13 preocupado

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Posted 21 February 2011 - 10:16 AM

Just wanted to let you know Ive been away for a few days, so I havent had a chance to carry out your instructions yet. Ill get back to you as soon as I do.

#14 Platypus

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Posted 22 February 2011 - 08:36 AM

That's quite OK.

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#15 MrBruce1959

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Posted 23 February 2011 - 10:54 AM

I am just adding another precaution here that needs to be addressed regarding the Zero Insertion Force flip levers on tape and reel type ribbon wires. Such as the ones you will have to flip open for the cleaning procedure.

The flip levers which lock down the flat multi-wired ribbon wire into place are very prone to breaking off at their hinges.
Once this happens, the connector is permanently damaged, hard to repair and the connection its self becomes almost non-existent. It in most cases requires a connector replacement, which can be very difficult to perform since the connectors have microscopic connectors that require a special technique to solder.

Please use extreme caution when flipping this locking lever up or down.

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