Lg 60pk590 half screen fault

[wreksta]

Hi all can you help I have this set I bought it cheap as gets half a screen only ie from middle to top
I replaced the top buffer board as It never heated the heat sinks at all on upper buffer

Bottom buffer heats up no problem
I've tested the y main all mosfets diodes check out

Could a test mode bring full screen on

I have checked the y board over and noticed 3 resistors that are located near where top buffer is someone has worked on them before as soldering is lumpy

Any ideas please

Y main part number EBR63450401


Upper buffer EBR71853501


Note if I unplug a ribbon from upper buffer I get a black line
So full screen is firing up just no picture on upper portion

[tom66]

Re: Lg 60pk590 half screen fault

Does the top portion of the screen have a slight glow?
You have tried a new buffer?
Pictures of the fault and board?

[wreksta]

Re: Lg 60pk590 half screen fault

I'm in no position to give pics at the mo

The top screen glows yes as if I unplug one flexi I get a big black line

Y buffer has been replaced yes

Any ideas tom

[tom66]

Re: Lg 60pk590 half screen fault

Well, I'll take a stab in the dark about the design then as LG are famous for changing the design of their plasmas quite regularly.

I'm assuming this has address boards only on the bottom, though I can't remember when LG changed the design from top and bottom to bottom-only on their large 1080p plasmas.

Since the top part of the panel is glowing, the buffer board is driving the panel and the scan voltages aren't shorted. However, no scan control signals are reaching that part of the panel, or the scan-high voltage (Vsc) is gone for those buffers.

A few possibilites:
- The resistors you see may be related to the Vsc path so check they match the value printed on them.
- Bad control board - not sending OC1/OC2 signals (reasonably rare)
- Bad logic buffer IC on Y-sustain or buffer (has happened before - but again rare)
- Contaminated connection/cold solder joint on connector
- Top buffer not sending chained signals to bottom buffer (has happened before, not that uncommon)
- Main board with some weird picture cropping (really don't think so but worth eliminating)

So possibilities break down to: Y-sustain, bottom buffer, top buffer, control board. To rule out the main board completely: jumper EXT AUTO GEN on the control board and unplug LVDS cable, you should get test patterns on the screen cycling through. (Make changes only with power OFF.)

Not much help I'm sure... If you have a scope, you can narrow it down by checking each of those signals and the outputs from the buffers and logic boards. Otherwise, the cheap TV becomes an expensive repair project. Sorry.

[wreksta]

Re: Lg 60pk590 half screen fault

Screen came on after a good few cycles of the auto ext gen I left it running now we have full screen with a faint line in centre which I think is screen burn or The fact it has only been running half screen for a while

Any help on this we updated software to get ten apps but no netflix any ideas
Or how to change the country to us I think I read somewhere

Thanks for the help


Hope the tv stays on normal been off a few times a screen returns so fingers crossed

[tom66]

Re: Lg 60pk590 half screen fault

So you're saying ext auto gen you get a full screen? That means the problem is 99% main board with a small chance of being control board or LVDS, but the chance is pretty minimal.

You can try loading new software from LG website with a USB memory device.

The half screen will be IR (image retention) run the TV on snow or a movie with a lot of movement like Avatar/Life of Pi for a day or so to remove it.

[wreksta]

Re: Lg 60pk590 half screen fault

Hi tom what I'm saying is I ran the auto for 20 mins and screen came on in full then I plugged in ldvs cable and removed jumper we had full screen and tv stayed on. This mornin I tried it and picture was halfed so left it 20 mins or so and it came on any ideas

[tom66]

Re: Lg 60pk590 half screen fault

Sounds like some thermal issue. Get out a hairdryer or hot air gun (max 100C) and start heating things up. If the picture comes back when you heat up a particular area try to narrow it down. Maybe control board BGA soldering issue.

[wreksta]

Re: Lg 60pk590 half screen fault

Hi tom still same issue I have even replaced the control board and still taking 20 mins or so to go full screen could the y main be at fault as there's two heatsinks on that that do not heat up for a good old while they are the right of yellow transformer any ideas could this be the panel or bonding

[tom66]

Re: Lg 60pk590 half screen fault

No pictures still so am asking again - single scan addressing or dual scan addressing?
If dual scan addressing boards have missing va this could cause faults like this.
I doubt it to be a ysus although it's not impossible it's a soldering issue.
The ysus usually drives both buffers with the same signals with a few exceptions.

[wreksta]

Re: Lg 60pk590 half screen fault

What do you mean by single drive or dual drive mate all I know is all voltages
Are correct and Ysus heat sinks two are cold till TV has been on bout half hour to an hour then those heatsinks get hot and then TV fires full screen any ideas

[tom66]

Re: Lg 60pk590 half screen fault

Well if you could supply a picture I could tell, it is hard to describe, address buffers on top and bottom of panel instead of ones just on the bottom. This is why we ask for pictures, every TV model (especially plasmas) are different sometimes even with the same model, is it so much to ask for even a camera phone pic...? Some X-buffers have fuses on them, or connectors that can come astray. Control boards can sometimes split the picture drive into two halves, which is apparent from how the control board is laid out (component and connector position, number of processor chips, etc.)

Heatsinks on a sustain board running cold isn't necessarily a problem - the panel will be running at less than half its rated power with a half screen fault, so the heatsinks might not be getting noticeably warm. Also, half the job of a heatsink is to effectively dissipate heat - the better it is at doing this, the cooler it runs, so it could just be an over-engineered heatsink. On my Kuro, the heatsinks get barely warm above ambient even after running for hours.

Since it is obviously intermittent, and this is almost always temperature dependent, I recommend you try to locate the temperature dependence by heating up parts. It would appear from your description that the TV gets better after time, so something will be heating up. Running hot air over parts may reveal exactly what is causing the fault.

And plasmas do not have tab bonding faults. One user reported a problem with a "plasma tab bond", but out of thousands here with no such issue, I'm tempted to believe it's a fluke.

[wreksta]

Re: Lg 60pk590 half screen fault

Here is some pictures for you tom

The two heat sinks in middle of the Ysus are the ones that stay cold

[wreksta]

Re: Lg 60pk590 half screen fault

Here is some pictures for you tom

The two heat sinks middle and bottom in the middle of the Ysus are the ones that stay cold

[wreksta]

Re: Lg 60pk590 half screen fault

Hi tom I found a few cold solder joins but still had a waiting game for TV to go full screen but it only took 5 mins each time if that I have found an area on the board can up pics shortly but it's the top right of Ysus it has the 3 copper coils

I heated this each time to bring time down for full screen I'm going to try running tv without heating it to see if it does it on its own

[tom66]

Re: Lg 60pk590 half screen fault

It is unlikely that the coils are bad, but perhaps the connectors nearby it. The coil connections going bad would affect the whole screen.

[wreksta]

Re: Lg 60pk590 half screen fault

This is the area tom any ideas where to start please mate

[wreksta]

Re: Lg 60pk590 half screen fault

Right waited till TV cooled and went went half with a hair dryer on full setting I aimed it at the main connector and tv flickered then bounced into full screen 10 secs or less

[tom66]

Re: Lg 60pk590 half screen fault

Poor connection? Clean all connections, make sure all pins seated, check solder connections.

[wreksta]

Re: Lg 60pk590 half screen fault

Any ideas what I could clean it with and if it is bad connection to age etc why would heating it bring it on

If it's soldering how am I to get behind there to there to redo as the main heat sink is in the way don't fancy taking that off to get to them I would rather hard wire