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Old 05-03-2022, 06:05 AM   #1
zen
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Default 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Hi all

Issue seems to be slightly tap sensitive , although that might be a complete coincidence .

Main board problem none the less .

Can anyone advise .

I'm leaning toward re-balling the main BGA processor chip .

Have the correct stencil in stock , therefore must have re-balled one of these chips in the distant past .
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File Type: jpg Main board.jpg (1.33 MB, 7 views)
File Type: jpg BGA.jpg (997.5 KB, 7 views)
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Old 05-03-2022, 06:31 AM   #2
Biruslapio
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

All signs point to BGA, I have one of these boards from a 42LM6400, after reflowing the main chip it lasted for 2 years, then further reflow attempts failed to make the TV last even 1 minute powered on.

But the TV should not freeze, it should power off immediately or not even get out of standby when it's the main chip.
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Old 05-03-2022, 07:28 AM   #3
zen
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Thanks for the input .

I don't tend to re - flow any more , as it doesn't seem to be reliable .

Will re - ball & report back
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Old 05-03-2022, 08:32 AM   #4
zen
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

On removal & inspection of BGA , may have worked out issue .

part of track , which looks to be a through hole point seems to have been exposed , by heat from the a capacitor that sits directly under it .

Could try some solder mask to insulate point then fit chip back .

Although it looks like it from picture it's not a pad .
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File Type: jpg Exposed track.jpg (663.7 KB, 17 views)
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Old 05-03-2022, 10:04 AM   #5
zen
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Re-ball seems to have gone really well , & solder mask to took exposed track .
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File Type: jpg re-balled chip.jpg (1.53 MB, 18 views)
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Old 05-03-2022, 11:19 AM   #6
zen
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Well i'm genuinely surprised .

Set powers & now working on a test .

Lets see how it behaves , or not a the case may be .
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Old 05-03-2022, 12:02 PM   #7
Biruslapio
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Nice job on the reballing process, hope it fixes it.
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Old 05-03-2022, 12:26 PM   #8
zen
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Thanks again
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Old 05-03-2022, 03:46 PM   #9
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Reballed a Vizio a couple years ago. Still working in the living room.
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Old 05-04-2022, 02:17 AM   #10
zen
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Nice one, yes re-balling rather than re-flowing seems to be the way to go for me .

Have been experimenting for a few years now & have quite a reliable technique with the equipment i use .

Many re-balling videos on You Tube .
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Old 05-04-2022, 11:27 AM   #11
dskall
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

I think leaded solder is superior to the brittle unleaded. Military still uses leaded solder for reliability.
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Old 05-05-2022, 02:50 AM   #12
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Default Re: 42LM670TZA , picture freezing , then powers off , or hanging on LG logo .

Most definitely .

Aviation also , & quite possibly medical equipment .

More work for us i suppose
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