Author Topic: 49uf680v flashing 3 times  (Read 334 times)

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dynomoman

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49uf680v flashing 3 times
« on: June 19, 2017,16:21:29 »
Got an LG 49uf680v that's flashing 3 times. Power supply fault or mainboard?  Set runs approx. 5 minutes then I see verticle white lines on picture then set goes off. Standby light flashes red 3 times. Set won't come back on for about 1 hour. Heat cold does not seem to affect fault.
« Last Edit: June 20, 2017,02:15:20 by dynomoman »

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49uf680v flashing 3 times
« on: June 19, 2017,16:21:29 »

downunder

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Re: 49uf680v flashing 3 times
« Reply #1 on: June 21, 2017,03:21:25 »

Hi dm,
Just an idea, since you mention vertical lines in the picture. The display panel may be at fault. So, disconnect one flexy cable that goes from t-con to panel. If you get a good picture in the connected half of the screen and/or the disconnected half is pure white, reconnect the flexy and remove the other flexy. Try the TV again. Report what results you get.

Bruce

dynomoman

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Re: 49uf680v flashing 3 times
« Reply #2 on: June 21, 2017,14:39:00 »
Hi Bruce,

Already been down that road. Unplugging ribbons from T con to screen makes no difference to the fault at all. 

Looks like LG has had a heat problem and used double sided taped and glued a nasty great alloy heatsink to a BGA chip on the AV board.  (see pic) Looks like a bad mod which they even taped to the back of the screen in case it fell off i guess. The heatsink is just a cut of alloy strip, not even a proper heatsink  :57:  I thought someone had made there own mod until I search for another board and they were all the same. I took the heatsink off and noticed the double sided tape was not makng much contact. To use that size heatsink on such a small BGA chip shows they were pushing the chip very hard.

Looking at the power supply voltages the PWR ON command is there at 3.5volts and the power supply comes to life when turning on from the remote. What i noticed the DRV ON which i guess is the command for the led supply to come on is there at around 3.5 volts and the set runs quite happy for about 3 - 5 minutes and displays a correct image. Then the DRV On voltage drops out to zero and the set turns to 3 blinking LED. All other supply seem to remain. 13.2 volts stays there nice and stable.

When the blinking is happening the chips on the t-con seem to still be still running as I can fell they are warmish to touch as well as the heatsinks on the main AV pcb are warm as well. I get no sound or picture during the fault. I have put a light to the screen but there is no activity. The only way the set comes back to life is to leave it for a few hours then you get another 5 minutes of run time. Heat, cold make no difference at all.

Mike
« Last Edit: June 21, 2017,17:31:16 by dynomoman »

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Re: 49uf680v flashing 3 times
« Reply #2 on: June 21, 2017,14:39:00 »

downunder

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Re: 49uf680v flashing 3 times
« Reply #3 on: June 22, 2017,05:19:23 »

Yea dm,

Getting heaps of LGs with this problem where the DVE-ON never appears or cuts out. Managed to restore some by cooking the main board, but others I had to get new boards or write them off. You're on the right track. If you link DVE-ON to SBY Volts you'll find the backlights will come on.

Bruce

dynomoman

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Re: 49uf680v flashing 3 times
« Reply #4 on: June 22, 2017,13:44:20 »

Yea dm,

Getting heaps of LGs with this problem where the DVE-ON never appears or cuts out. Managed to restore some by cooking the main board, but others I had to get new boards or write them off. You're on the right track. If you link DVE-ON to SBY Volts you'll find the backlights will come on.

Bruce

Good minds think alike. I thought of linking those lines as a test too. I am trying to find a main board but no ones got one in stock so far.   

Thanks for the replies Bruce !

dynomoman

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Re: 49uf680v flashing 3 times
« Reply #5 on: June 30, 2017,15:10:13 »
Managed to get a scrap set with smashed screen. Changed over mainboard and we are up and running again. I have noticed 2 small white spots on the panel have arrived. Maybe bad pixel not sure but the tv is working ok now.

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Re: 49uf680v flashing 3 times
« Reply #5 on: June 30, 2017,15:10:13 »

downunder

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Re: 49uf680v flashing 3 times
« Reply #6 on: July 01, 2017,03:16:11 »

Possibly a couple of the lenses that fit over the LEDs have fallen off. That would make the screen in front of the offending LEDs appear brighter.

Turn the TV upside down and see if anything rattles.                       Bruce

dynomoman

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Re: 49uf680v flashing 3 times
« Reply #7 on: July 02, 2017,04:43:12 »
Hi Bruce,

Looks like a few stuck pixels rather than a bright spot to be honest. Pixels stuck white in 2 small regions.

downunder

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Re: 49uf680v flashing 3 times
« Reply #8 on: July 02, 2017,05:03:26 »

More likely dead pixels. Stuck pixels show a colour. Dead pixels are a solid white. Wouldn't that just rot your socks. Is it so noticeable?

dynomoman

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Re: 49uf680v flashing 3 times
« Reply #9 on: July 02, 2017,06:26:01 »
It's not to bad to be honest when a picture is displaying.  Strange they were not there before the motherboard died. I took a picture and you can see several displaying pixels in white. Its not as bad to my eyes compared to what the camera see's. I wondered if the motherboard is doing this ?

I have not fired a BB gun at it  :s_laugh:

Oh well :)
« Last Edit: July 02, 2017,06:54:20 by dynomoman »

downunder

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Re: 49uf680v flashing 3 times
« Reply #10 on: July 02, 2017,20:05:08 »

Nah! Main board/T-con would cause lines and the non-linear pattern of the white spots would exclude the backlight LEDs. Has to be a panel fault but you could try refitting old main board and see if they're still there. I've not seen one like that and I think you're right, the pixels are locked on. A few articles on the net about fixing stuck pixels may be worth a gander at.                       Bruce

 

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