LG 50PK590 green background colour

[Rokster]

A few days ago I started noticed areas of green on the television screen. Upon closer inspection it seems that the background colour of the screen is now green instead of black and everywhere that should be displaying black (presumably by not displaying any coloured pixels atop the background), the colour green is showing.

This isn't happening all of the time but it is happening most of the time.

It's happening on all inputs - game consoles, aerial, Fire Stick, etc. I've tried disconnecting all inputs other than the standard aerial and the problem persists.

I've tried resetting the TV to default settings and turning the TV off and then on at the mains.

I've had a television engineer over who tried replacing the timing controller (t-con?) board but with the same results. He suggested, as that wasn't the problem, it probably wasn't repairable.

I was wondering if anyone else had suffered the same problem and if there might be a different possible cause?

[tom66]

Re: LG 50PK590 green background colour

There are several possible causes, I would suggest the LVDS cable (which runs between the main board and control board - the plasma equivalent to the "T-con") or the main board.

If you feel like taking the back of the TV off, we can do a simple test that can reveal if the issue is with the mainboard, or elsewhere.

[Rokster]

Re: LG 50PK590 green background colour

If it's going to save replacing a nice TV that might be able to be repaired then I'll happily take the back off it. I'll have to do it after work this evening. What will I need to do once the back's off?

[tom66]

Re: LG 50PK590 green background colour

Take good clear pictures of the whole TV circuit board layout and one of each main circuit board. There are many circuit boards. Don't worry about the ones for the infrared or anything that's buried, just the obviously visible ones.

You can usually service these TVs with the stand on, so don't take that off (or put it on if it's wall mounted). The bolts will usually need to be out, but usually the stand bracket will hold the TV in place.

Do you have a multimeter?

[Rokster]

Re: LG 50PK590 green background colour

I'll need to (a) find the stand as it's wall mounted and (b) purchase a multimeter. I can do the latter through Amazon Prime so should be able to get one for the weekend. Looks like this will be on hold until possibly Monday then, but I'd certainly like to do the testing when I'm in a position to do so.

[tom66]

Re: LG 50PK590 green background colour

We can hold off for the multimeter for now, as it's not needed for the first test. It would be needed if further diagnosis is required.

You don't need the stand if you can prop it against a sofa or something similar, it's just a lot easier because ideally you'd be able to see the screen for this test.

[Rokster]

Re: LG 50PK590 green background colour

Ok, this sounds like a plan. Though I'll have to remount it after the first test while waiting for a multimeter to arrive if it comes to that.

What will I need to do? Or is this where you'll need the photos first to proceed?

It'll likely be three or four hours before I get chance to dismantle the TV this evening.

[tom66]

Re: LG 50PK590 green background colour

Just take the back off (there will be a lot of screws) and get nice clear, focused pictures of each board. I don't have this TV in front of me, so I'll need these pictures as my eyes.

[Rokster]

Re: LG 50PK590 green background colour

Ok. I'll get the photos sorted this evening. Thanks very much for helping with this.

[Rokster]

Re: LG 50PK590 green background colour

Let me know if you need any other (or better) photos and I'll get them sorted straight away

[tom66]

Re: LG 50PK590 green background colour

Thanks for the pictures. They are good.

We need to see what is going on with the control board, please follow the steps below.

1. Unplug the TV and wait a minute for everything to discharge.
2. On this board (attached), you will see two holes. Place a jumper wire between these holes. Could be a bent paperclip, a piece of wire... Make sure it's shorting these holes together and nothing else.
3. Disconnect the highlighted connector. (Squeeze the edges and gently tug on it)
4. Prop the TV up so you can see the screen.
5. Plug the TV in. CAREFUL! There will be high voltage exposed on components inside the TV, do not touch anything inside the TV while the set is plugged in.
6. If the TV is in standby, use the remote control to turn it on.
7. You should see a series of test patterns cycling on the display. Try to see if the green issue is present with these, you may need to darken the room. There is a pattern in the cycle that is black; use this in particular to tell if there are parts of the screen that are green.

Example of the test patterns (yours may vary): https://www.youtube.com/watch?v=9LcqLM5TRHk

[Rokster]

Re: LG 50PK590 green background colour

Interesting set of eye boggling test patterns - plenty of pure black and no signs of errant greenness.

I mentioned that there were occasional periods where the tv was still working as it should. But they were generally pretty fleeting so hopefully this wasn't a fluked test pass.

(As a side note, when watching normal television the greenness has been the full screen - or, rather, any blackness anywhere on the screen would be green. It hasn't seemed to affect only parts of the screen)

[aaronwt6]

Re: LG 50PK590 green background colour

Assuming that the past test was not just a fluke (as you stated), that would point to the main board as the issue. That's the one with all the input jacks (A/V, HDMI, ect.).

If you search for a replacement, use the number on the yellow sticker (EBT61039402). Do not use the EAX number that's stamped on the board itself. You may be able to locate someone that can service the board as well. Not sure on the cost over there of service or replacement. Tom may chime back in with an idea.

[Rokster]

Re: LG 50PK590 green background colour

We recently purchased an Amazon Fire Stick and, because of the difficulty in accessing the HDMI ports behind the television when it's wall mounted, have been swapping cables in the HDMI port on the side fairly regularly between the Fire Stick and the Steam Link. Maybe that could have put extra stress on the main board? (Though I'd like to think they're designed to cope with HDMI cables being plugged in and unplugged).

[aaronwt6]

Re: LG 50PK590 green background colour

I doubt it, but I'd never advise frequent swapping on an HDMI port. Especially not with the TV powered on. You might want to consider an extension from one of the other ports to plug the fire stick into. You can even purchase a 90 for the HDMI if space won't permit plugging something into one with it wall mounted.

[tom66]

Re: LG 50PK590 green background colour

Cool. Looks like the main board is faulty.

Something you can try before swapping the main board is removing the LVDS cable, cleaning it using some contact cleaner on both ends, then testing the TV again. You need to connect the cable both ends and remove the test jumper.

In fact, provided you feel safe enough with your hands behind the TV (or perhaps use a plastic/cardboard tool) try flexing the cable back and forth to see if it has an intermittent fault. Coloured tinges can happen with failed LVDS cables; I'm not exactly sure of the cause but it's a fairly common fault.

[Rokster]

Re: LG 50PK590 green background colour

Thank you so much for all of your advice! I'll try the cable cleaning and wiggling tomorrow as it's getting pretty late over here now. This has been fun, educational and very, very useful.