LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter scenes

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

I am almost considering perhaps a software problem?
How does changing things like the brightness settings affect the problem?
Does LG have a firmware update available?

I just deleted a draft response to this Tom, sorry.

In short; The LD920 is shipped with standard v3.0 software, with no updates available. This is because LG pulled the TV from the shelves to sell to industry (hotels etc) shortly after release.

The successor, the LD950, has a few updates. One LG USB wiki page suggests that one can use LD950 firmware, but according to 2 users on an AV forum owner's thread, it causes major problems.

Regardless, my gut says this isn't a software problem. I would be happy to reinstall original firmware just to test, but it's not available anywhere.

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

I used to have access to LG's service site with firmware but the trick I used got patched. I'd help you if I could... It may also be possible to use the LD950 main board if the rest of the TV is similar enough.

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Shame! Ah well. Check that previous post of mine too..

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Interesting that colour affects it. Quite possibly some processor function is having difficulty.
Have we tried service reset yet?

MENU key on set and MENU key on remote for 5~10 seconds.
Then select reset option (may be buried in menu.)

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Also, turn off "XD Engine" and "Sharpness" options, to see if those have any effect.

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

OK, this is weird..

I can't seem to activate the service menu via any of the 3 standard methods.

Nothing changes onscreen. I've got another LG, so I know what should be happening..

Remote batteries are fine. And, by holding down MENU on remote, the OSD does disappear after a few secs, but is not replaced by a service menu.



Method 1
Press and Hold <OK> button on remote as well as TV panel at the same time for a few seconds.
Method 2
Press and hold the {MENU} button on the remote and the {MENU} button on the TV at the same time for at least 5-7 seconds.
Method 3
Press and hold the {MENU} button ON THE REMOTE until a 4-digit password screen is displayed.

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

OK, in the meantime I found Factory Reset in the normal menu, but no change.

This service menu access problem is strange tho..

Regarding sharpness etc, I experimented with all, on and off. Seems like it's exclusively affected by large amounts of certain mixed colours.

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Try MENU, 3, 1, 4, 1, 5, 9. People have had luck with that one instead.
A geeky LG engineer must have included that one...

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

MENU, 3, 1, 4, 1, 5, 9.. nothing!

what on earth's going on?

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Have you tried from power on? Unplug TV and hold buttons, then power on.

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Tried all 3 methods as suggested, plus MENU, 3, 1, 4, 1, 5, 9. Nothing..

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

I'd say something is up with the firmware or settings then but I wouldn't know how to fix that.

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

If it's a firmware bug, it only started occurring a few weeks after I purchased it, after it belonged to the previous owner for about 13 months.

But admittedly, the fact I can't access the menu is pretty worrying..

I found a guide to program a Logitech Harmony remote as an LG Service remote, which has helped a few who had similar problems - I'll give this a try in the morning, along with more heat tests and a more thorough dismantle/connection check.

Time for bed now, though.
Thanks for your help, Tom. I'll report back tomorrow.

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Hi Tom,

Been a while, but I've found some spare time. If you don't mind, I have a question. Something happened during my tests this eve.

Could a hairdryer be enough to cause a reflow, or to fix a dodgy board?

-I put aside some time tonight (and tomorrow) for another diagnosis session.
I wanted to prove/rule out your firmware-bug hypothesis, so I ran some more heat tests, this time on the (unknown) board between AV board and T-CON.

-Last time, tests appeared to indicate that heating the AV board caused increased blink frequency, so I replaced it. Problem continued.

-This time, I wanted to rule out that residual heat may have actually been affecting the nearby (unknown) board between AV board and T-CON, so I tested it with a more focused heat (a hairdryer instead of fat portable heater).

-Initially I thought I had success; Blinks every 8s with no heat, frequency increasing to 3.5s after 20 seconds of heat, decreasing steadily to 4.5s after 2 mins with no heat.

HOWEVER...
I'm currently unable to run further tests - because for the time-being, and for the first time, the problem has completely gone away! All the colourful screenshots I saved, which were previously guaranteed to get the set blinking, are failing to have any effect whatsoever.

Its actually frustrating, as I need more demonstrative evidence that this unknown board is the problem. So in the meantime, I wondered if you could tell me whether the heat might have temporarily solved things, as per my opening question.

If so, I'll probably order a replacement board at try a reflow with the current one in the meantime.

Pic of board attached.
EDIT: Just looked at the details on the board, EAX6167901 (3). I'll search for this part now.
EDIT: Having trouble finding out what this board is! Google isn't helping. Any idea?

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Huh. I did not realise this chassis had a second t-con. A picture of the overall layout could have eliminated such confusion.

Heat can definitely temporarily repair solder joints, so you can try a proper reflow on that board if the problem returns.

I don't know what that board does. I'd take a guess it's some kind of format converter, or perhaps motion interpolation (100/120Hz?)

[Stimpers]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Post #12.

www.4ourhouse.co.uk got me the AV board last time, hopefully they can trace the mystery board using the EAX number.

Cheers as always, Tom. Thanks for the prompt response, enjoy your evening.

[tom66]

Re: LG 47LD920 Display (not backlight) blinks off every 8 seconds during brighter sce

Post #12.

www.4ourhouse.co.uk got me the AV board last time, hopefully they can trace the mystery board using the EAX number.

Cheers as always, Tom. Thanks for the prompt response, enjoy your evening.

Ignore me. I forgot about that. Hmm, it would definitely point to that board.