LG IPS237L ... image retention, get pink, ...

[saronno]

Hi,
I have some strage issue in a LG IPS237L.




As you can see I have persisten image,
sometimes it get pinkish
and on the left part of the panel it looks like
there are "missing lines" ... the last issue is very difficult
to catch with the cam.

Of course I just checked the lvds cable.

These issues are present with all the inputs (2 HDMI and 1 vga)
and whatever source you use (bluray, pc, laptop) ... so it is
something the board or on the panel.

have you ever had any issue like that?


TIA

[ReeceyBurger123]

Re: LG IPS237L ... image retention, get pink, ...

Delete.

[saronno]

Re: LG IPS237L ... image retention, get pink, ...

Update: I have managed somehow to solve the color problem (It doesn't get pink anymore .. substantially reconnecting all the cable), but a little problem have remained:
I put a totally blank image on the monitor and I don't get a full blank image in the last
10 cm on the left. If you check carefully, you have a pattern with one line of pixel fully
blank and another greenish .... if you move to the right, the greenish line fade to blank
(in other words it's not a net transition, but a slow change to blank).

I also check the flex connectors that go directly on the matrix putting some pressure on
the glued connection and also tried to put pressure on the driver ... nothing.

[saronno]

Re: LG IPS237L ... image retention, get pink, ...

Good one:


Bad one:

[saronno]

Re: LG IPS237L ... image retention, get pink, ...

This german user seems to have a similar problem on the same model:
http://extreme.pcgameshardware.de/mo...-ips-237l.html

and also this polish guy:
http://www.elektroda.pl/rtvforum/topic3183348.html

[saronno]

Re: LG IPS237L ... image retention, get pink, ...

same problem also here ...
http://www.elektroda.pl/rtvforum/topic2889170.html

It seems a pretty common issue with this model.

[saronno]

Re: LG IPS237L ... image retention, get pink, ...

Anyway, thinking about it, I suppose that the voltage
level on the selected rows is not good enough and so,
the transistors don't open completely .....
so, when you apply the pixel by pixel tension (column)
you can't charged (and discharge) completely the cell.
I image that the row has its own resistance and that
in the first part the voltage is good enough to open the gate
of the transistors ....but going from right to left
the voltage is lesser and lesser and so those gates don't
open the transistor completely...

Solution? Raise up the voltage feeding those rows ...
I check tha panel datasheet ... if I am right it's not
a main board problem but a problem on the pcb of the panel.

Very difficult to repair (it's very easy to do a damage) .... but maybe not impossibile.

[saronno]

Re: LG IPS237L ... image retention, get pink, ...

With a VDD of about 12V
is a VCOM of 4.2V a bit too low?

Is it the probable cause of image retention?

If so, since the is no pot to adjust it ... is it programmable
from a secret menu ?