LG LCD monitor problem

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I have a 3 month old LG Electronics monitor (L226WTQ).  Yesterday, I
noticed a vertical line, all the way from top to bottom, about 1 inch
from the right of the screen, which seems to be present in all modes.

Is this a returnable fault or is there something I might be able to do
to get rid of it?  The line appears to be about one or two pixels wide
and is present during boot, and when operating in both digital and
analog modes.

I have tried reconnecting the video cables, switched the electrical
source, and changing resolution with no effect.  It almost seems like
one wire in the monitor is no longer carrying a signal.


Re: LG LCD monitor problem

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Other than "whacking" it with your hand, it sounds like a warranty issue to

Re: LG LCD monitor problem

Clark wrote:

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have you tried pressing autoset

Re: LG LCD monitor problem


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I would expect that it is still under warranty at the 3
month point.  Therefore, it would be best to RMA it instead
of opening it up (voiding the warranty) to check for
intermittent electrical connection(s), though I also suspect
it could be a *wire* or other disconnected signal path.

Re: LG LCD monitor problem

Sounds like an internal fault, without seeing the actual display it's
difficult to say   but it does sound like a drive data fault on the
display section.

Modern displays don't use vertical amplifier's or horizontal scanning
circuits, in which case I would have suggested a fault or something
affecting the vertical drive waveform.

Having said that many a strange fault has been cause by the ribbon
cable that connects to the front display section in 'flat panel

Best bet is to try another monitor or try the monitor elsewhere just to
ensure it is the monitor at fault.

If it is the monitor the best option would be to return it since it is
new and should be covered by warranty.


Re: LG LCD monitor problem

davy wrote:
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I think it is a matrix (rows and columns), driven by chips like these.
Multiple chips are required to handle the large number of rows and


Chances are, a single output pin on one of those chips is defective,
and that is why a vertical line appeared on the screen. I expect there
is a scanning process to how LCD screens work, as each node is a capacitor
that must be recharged at regular intervals. So a whole column is recharged
at a time (column chip activates whole column, row chips charge all cells
in the column to specific voltages, so 1024 elements get charged at a time).
As the capacitance discharges, the appearance of the pixel would change,
and so it must be refreshed often enough, that it is not visible to the user.

To complicate matters, the nodes can have no net DC across the cell, so
in fact the capacitor has alternating voltage placed across it, first
some V+ and then V-, such that there is no net DC across the liquid
crystal chemical. Otherwise, the chemical rapidly breaks down. Now, that
could mean charging 120 times a second, to get a 60Hz frame rate.

I'm still looking for an accurate description of the whole process. (I'm just
going by articles that describe the thin film transistors and how they work,
and the rest is supposition on my part.) I've downloaded a few panel datasheets,
and they never ever go into details at the physical level.

There is another document here, if you are interested. In this document,
rows and columns are called backplanes and foreplanes. See page 9 for
sample waveforms. I'd prefer to find a document with this level of
detail, only focusing on the large panels used on computer monitors.



Re: LG LCD monitor problem

Thanks for the replies.  I called the local warranty repair shop and they
said it was probably one of two things.  One was fixable in shop and the
other would have to be returned.

I'll post back when I know for sure.  Hopefully this is just a fluke and not
a problem with the LG monitors.


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Re: LG LCD monitor problem

Clark wrote:
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Just an update, I took the monitor to an LG approved repair shop and
have not heard anything for 3 1/2 weeks.  They won't even call back to
let me know the status.

I think LG and I are going to part company after this mess!


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