LG W3000H distortions after a short while

[mastakilla]

Hi All,
I have this 30" LG display, its story is as follows:

- worked flawlessly for 4 years, then a 200 pixels high horizontal band on the bottom of the screen started acting funny: it would freeze, then slowly become washed out, then black.

- had it repaired by an official LG shop, they changed the logic board and it worked fine again for about 1 year. A thing I've noticed immediately is that after the repair, while disconnected from a signal, it would cycle red, green, blue, white. Beforehand it would just stay black so I think that they have changed something, in fact.

- some days ago, it started producing black flickering random lines/garbage from around 2/3 of the screen height down to the bottom.
Along with flickering, I get very fast tilting and portions of screen copied around randomly. The defect is there even if disconnected from a signal.

The defect seems to be heat related as it works fine for a while (30 secs - one minute) when turned on from cold.
I have already replaced all the caps I could see on the PSU board and signal board...except the two with a red dot on the PSU.
Note that I think the first LG center swapped my psu with another as it hat 2013 written on it while the monitor was purchased in 2009

what should I look at now??

Many thanks!!

[mastakilla]

Re: LG W3000H distortions after a short while

Today I have tried reflowing the tcon board by baking it in the oven at 200c for 10 minutes, but it didn't work.
I have also put some rubber seal behind the little elongated things that are sandwiched in the flat cables of the lcd, as I've seen done in a video somewhere...again, no perceivable difference.
I'll buy another 30" (Iyama maybe?) and try to have this repaired by the shop for a fair price, otherwise it's going in the bin

[Agent24]

Re: LG W3000H distortions after a short while

Could be the logic board has gone bad again.

I doubt its the panel though.

Check the PSU voltages are all OK, try swapping TCON and mainboard perhaps, could even be a broken LVDS or similar cable.

If you get rid of it, you could always sell it as for parts and make something back on it.

EDIT:

The defect seems to be heat related as it works fine for a while (30 secs - one minute) when turned on from cold.

I see thermal paste on one of the chips on the TCON board but no heatsink. Did the heatsink fall off and now the chip is overheating?

[mastakilla]

Re: LG W3000H distortions after a short while

The thermal paste you see is what remained on the chip after an attempt to cool it with a cpu heatsink (which made no difference), originally it had none.

I ended up carrying it to the shop which will quote me a repair: they said that it could be the tcon...who knows.

I fear that once they'll see the slightly melted inductors on the logic board (as a result of my diy oven reflow attempt) they'll want to change it even if it is not faulty at all
Anyway, thanks for the inputs: I will let you know how it goes.

[mastakilla]

Re: LG W3000H distortions after a short while

I've had this monitor for literally years in pieces, can't bring myself to throw it away, so I'm giving it another go!
I've seen some videos of how the pros lay their lcds on transparent tables with a backlight to diagnose issues, so tried the same. All the boards neatly laid out on a table, lcd on a transparent sheet of polycarbonate with some led strips below.
Doing so I've discovered that the panel *works*! I've just noticed a hint of flickering once when just turned on, otherwise I've left it for hours and it's been faultless.
The only difference is that I've not hooked up the inverter board and the ccfl backlight.
Can it be that something is failing there causing issues elsewhere? From my understanding a fault inverter board results in dim/no backlight.
Another thing I've noticed is that some small voltage regulators on the tcon seem to get pretty warm, but maybe it's normal.

[mastakilla]

Re: LG W3000H distortions after a short while

Well the sad story of this monitor has finally come to an end.
I've finally pinpointed the issue: it was not the tcon, psu or cfl inverter. It was indeed the panel, and specifically one of the side COF chips that went bad once heated.
When mounted inside its case, with the backlight warming everything up, it started misbehaving after about 5 minutes, while out in free air as I was testing it, it could go on indefinitely but a quick blast of hot hair would quickly reveal the fault.
I tried to fiddle with it applying some pressure to see if it changed anything, and in doing so I've managed to break the thin chip in half.
As a last resort, I've stripped all 4 the side COFs as I've seen that sometimes with other panels this worked, but in this case resulted in a uniform black screen, probably because on this panel they are not redundant, there's nothing on the other side.