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Hi, I have a strange issue with a LG monitor.
At first, it have persistent images and get "pinkish".
I cleaned the lvds cable and situation get better.
Anyway, I still have persisten image on the left. Besides,
if you watch carefully with a magnifying glass you will see
that the problem is only on "odd" rows ... in other words
one row is fine but the next one have and issue (less brighter
on all the three colors)... and again, good, bad, good, bad ...
right side (it's perfect):
left side:
I am not a tft expert, but my guess is that the line opening the gates have
a voltage a bit below standard and so, in the left part on the screen, it doesn't
open completely the transistor (the line has its own impedance so the voltage is not exactly the same along the row). This happen only on "odd" rows .. probably because the voltage on odd and even rows are independent of one another.
Am I right?
If so, I think I should check VGL, VGH and Vcom ... right?
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Member Rasz should be able to offer good advice when he sees your thread, maybe you could PM him and provide a link to it.
https://www.eevblog.com/forum/profile/?u=12153;area=summary
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bad panel
iv seen similar effects where backlight slowly cooks the glass -
bad panel
iv seen similar effects where backlight slowly cooks the glass
Even if the panel has a led backlight?
Anyway I send a PM to Dave ... I will try to play with VGL/VGH/Vcom just to see how it will react
and have some fun. I don't have the schematics of course, but I don't think it will be so hard to find
the right feedback resistor to change these voltages playing with a potentiometer. -
bad panel
iv seen similar effects where backlight slowly cooks the glass
Even if the panel has a led backlight?
especially, there are lg panels with led string only on right side (afair), and with time that right side goes yellow with weird every second row dimmer effect -
bad panel
iv seen similar effects where backlight slowly cooks the glass
Even if the panel has a led backlight?
especially, there are lg panels with led string only on right side (afair), and with time that right side goes yellow with weird every second row dimmer effect
Good to know ... I will also check where the led stript is located on this model ... -
However it's not a intuitive idea ... it's strage having this issue on alternate rows, isn't it?
Why not all the rows? -
However it's not a intuitive idea ... it's strage having this issue on alternate rows, isn't it?
Why not all the rows?
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Thanks, nice video.
Anyway, in my case, the issue is on the other side ... so,
the cause could be something external (maybe a lamp or something
heating in the nearby). -
I agree, bad panel. I've seen a lot of bad panels recently, it seems like 75% of the warranty dispatches we get are bad panels.
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I agree, bad panel. I've seen a lot of bad panels recently, it seems like 75% of the warranty dispatches we get are bad panels.
How many of them are "real bad panel" ? Since the TCON is integrated with the panel (connected with the tbond) maybe
some of them are not real bad panels ... ? -
Well, given it's pretty much impossible to replace the TCON it's considered part of the "panel"...
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Well, given it's pretty much impossible to replace the TCON it's considered part of the "panel"...
replace is impossible but sometimes the tcon is fixable. -
This afternoon I made some test, just for fun ....
I got to integrated TCON ... first thing I saw were a couple of intriguing test points
... vgh_o and vgh_e ... these made me think that alternative row
has different vgh source (o and e I think stay for odd and even).
I check them with the multimeter .... they alternate from 30v to -8.5v ,,, fine ...
ops ... just a moment, wtf, how could I see this with my multimeter??? Aren't
they suppose to do that at a certain frequency? So I took the scope ... and this is
what I got:
Second per division was 5.
How come is it so slow??? -
is it 4V a bit too low for VCOM?
I didn't find AVDD, but VDD is about 10,7V ...
VCOM should be about AVDD/2 .... right?