LG Picture Fault


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LG Picture Fault

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redmatt8
New User

May 13, 2013, 1:52 PM

Post #1 of 4 (1591 views)
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LG Picture Fault	Can't Post

Hi All
I have a LG 42 inch LCD with a recent fault, on start up the picture was as should be, but after about 5 mins the picture turns really bright, ive gone through all the settings on tv menu, lowered brightness contrast etc, which you can see was having an effect on the picture, but not enough as it still looked like its washed out ? i was told the Inverter Board was at fault which in this case there was 2 of them, so i replaced them both with like for like and its made no difference at all, or could there be a fault with the LDVS Board, but as the brightness contrast etc was making a small difference mean that the board is okay ?
Would appreciate any wisdom
Matt.

74f100
Enthusiast

May 15, 2013, 4:20 AM

Post #2 of 4 (1568 views)
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Re: [redmatt8] LG Picture Fault [In reply to]	Can't Post

Lg made quite a few 42 inch lcd's. Do you have a model?

Also, what input are you using? And what happens if you change input?

Good luck,
Jim
HDMI not working

redmatt8
New User

May 15, 2013, 12:05 PM

Post #3 of 4 (1562 views)
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Re: [74f100] LG Picture Fault [In reply to]	Can't Post

Hi Jim, Its a 42LG5000-ZA LCD. <br>The problem is on all inputs wether its satellite box, dvd, vcr freeview or games consel either HDMI, Scart or RF <br>Also on going through picture settings, Advance Control i cant adjust the Black Level ? the inverter board and the AV input Board has been replaced now with no change at all, it only leaves the LVDS and PSU boards which would be the most likely PSU as it supplies the power voltage or LVDS which supplies the signal to the tubes ? <br>

(This post was edited by redmatt8 on May 15, 2013, 12:06 PM)

74f100
Enthusiast

May 16, 2013, 1:17 AM

Post #4 of 4 (1546 views)
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Re: [redmatt8] LG Picture Fault [In reply to]	Can't Post

That model doesn't ring any bells.

Look for a small ribbon cable leading from the timing control to the inverter. On some LG models, there was a comparator circuit that compared video levels going into the T/C and varied the brightness to the inverters.

I would consider that more likely than either power supply or LVDS (actually almost 0 chance of those being the problem).

Also monitor the burst voltage going into the master inverter. It will be labeled differently, but it will be right next to the BL on pin. When the picture is normal, note that voltage, when it messes up, note the voltage.

With that info, I'll check the service lit. and we'll get to the bottom of the problem.

Good luck,
Jim
HDMI not working

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