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Old 01-11-2017, 02:17 AM   #1
jondoe
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Default LG 37LD490 - Glitching picture.

Hello bad cappers

I have been given a sickly LG 37LD490 with a glitching/tearing picture that improves as the tv warms up, but never quite clears up, also the HDMI ports don't seem to work. It powers on fine, gets past the LG logo to the spinning LG cube, you can enter the menu, etc, although I don't have the remote

The power supply output looks like this;

NC | Error
12v | P-Dim
12v | A-Dim
12v | INV ON/OFF
Gnd | Gnd
Gnd | Gnd
3.5v | 3.5v
3.5v | 3.5v
Gnd | Gnd
Gnd | Gnd
20v | 20v
Pwr On | 20v


The 12v output is running at 12.3v, the 3.5v is at 3.4v and the 20v is 21v. My assumption here is that is in reasonable spec. No visibly nasty parts, everything looks "normal". Attached are pictures of the three main boards and my furry diagnostic assistant.

I gather from googling that re-flowing might be in order? Any tips gratefully accepted.

Thanks.
Attached Images
File Type: jpg IMG_2476.jpg (973.6 KB, 24 views)
File Type: jpg IMG_2477.jpg (632.9 KB, 8 views)
File Type: jpg IMG_2478.jpg (942.9 KB, 11 views)
File Type: jpg Cat_2475.jpg (509.9 KB, 31 views)
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Old 01-11-2017, 07:03 AM   #2
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Default Re: LG 37LD490 - Glitching picture.

Reflow mainboard.
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Old 01-11-2017, 07:50 AM   #3
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Default Re: LG 37LD490 - Glitching picture.

Given the very poor implementation of the heat sink on the XD chip, I'll start there. The sad part is you can see the PCB has been designed to take a heatsink MUCH larger, but they opted for a 2/3rd's option, leaving some of it uncovered, that can't do it any favors.
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Old 01-11-2017, 07:54 AM   #4
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Default Re: LG 37LD490 - Glitching picture.

Try a relow as reece suggests as your hdmi ports dont work when you get a remote control try a factory re set if that does not solve the hdmi issues maybe look for a replacement mainboard just get one with all matching numbers etc.
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Old 01-11-2017, 08:02 AM   #5
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Default Re: LG 37LD490 - Glitching picture.

I'm going to try and find a larger heatsink in my spare parts bin, a passive cooled graphics card would be suitable I suppose. Anything is better than the LG supplied one

Using a cheap rework air station, picture attached
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Old 01-11-2017, 08:14 AM   #6
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Default Re: LG 37LD490 - Glitching picture.

if you had some liquid flux it may help too with a longer lasting repair
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Old 01-11-2017, 08:18 AM   #7
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Default Re: LG 37LD490 - Glitching picture.

Ive done several of these boards seems both processors can have bga issues causing lots of different symptoms Ie no sound on hdmi etc. So might be best to do both of the heatsunk ones. Fucking shit from lg they run soo hot and thats the only heatsink they add so small and weak. I use silicon thermal plaster to add new heatsinks.
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Old 01-11-2017, 08:29 AM   #8
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Default Re: LG 37LD490 - Glitching picture.

vinceroger69 - I only have very fluid flux, not the nice thick stuff, I need to order some soon. I applied a little around the edges but most of it had evaporated by the time I'd finished.

ReeceyBurger123 - I've found a nice AGP graphics card with a heatsink four times the size, just need to find some sticky back thermal silicone.


I cooked her gently for 10 minutes at 300 degrees, currently letting it cool down by the window, will test shortly.
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Old 01-11-2017, 08:42 AM   #9
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Default Re: LG 37LD490 - Glitching picture.

Ok dont apply heatsinks unless it works can run it shortly with them off
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Old 01-11-2017, 10:55 AM   #10
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Default Re: LG 37LD490 - Glitching picture.

So far so good, display working perfectly, USB file playback working, dvi to hdmi port 1 working. Have left it turned off for the evening and will test at length tomorrow ��
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Old 01-11-2017, 01:25 PM   #11
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Default Re: LG 37LD490 - Glitching picture.

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Old 01-12-2017, 01:45 AM   #12
jondoe
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Default Re: LG 37LD490 - Glitching picture.

After a night to cool down she's fired up fine this morning, a day of testing awaits her.

Attached is a picture of the proposed heat sink, the old one is off the board for comparison. It still gets so hot, you can barely touch it, but I'm hoping the extra surface area and complete chip coverage will help with the longevity of the repair.
Attached Images
File Type: jpg IMG_2481.jpg (758.9 KB, 30 views)
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Old 01-12-2017, 03:28 AM   #13
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Default Re: LG 37LD490 - Glitching picture.

Quote:
Originally Posted by jondoe View Post
Hello bad cappers

I have been given a sickly LG 37LD490 with a glitching/tearing picture that improves as the tv warms up, but never quite clears up, also the HDMI ports don't seem to work. It powers on fine, gets past the LG logo to the spinning LG cube, you can enter the menu, etc, although I don't have the remote

The power supply output looks like this;

NC | Error
12v | P-Dim
12v | A-Dim
12v | INV ON/OFF
Gnd | Gnd
Gnd | Gnd
3.5v | 3.5v
3.5v | 3.5v
Gnd | Gnd
Gnd | Gnd
20v | 20v
Pwr On | 20v


The 12v output is running at 12.3v, the 3.5v is at 3.4v and the 20v is 21v. My assumption here is that is in reasonable spec. No visibly nasty parts, everything looks "normal". Attached are pictures of the three main boards and my furry diagnostic assistant.

I gather from googling that re-flowing might be in order? Any tips gratefully accepted.

Thanks.
Excuse my ignorance, but what does the NC stand for. nc for no connection, and NC = ?
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Old 01-12-2017, 04:19 AM   #14
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Default Re: LG 37LD490 - Glitching picture.

Quote:
Originally Posted by Grunder View Post
Excuse my ignorance, but what does the NC stand for. nc for no connection, and NC = ?
Not Connected.
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Old 01-12-2017, 07:57 PM   #15
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Default Re: LG 37LD490 - Glitching picture.

Quote:
Originally Posted by jondoe View Post
After a night to cool down she's fired up fine this morning, a day of testing awaits her.

Attached is a picture of the proposed heat sink, the old one is off the board for comparison. It still gets so hot, you can barely touch it, but I'm hoping the extra surface area and complete chip coverage will help with the longevity of the repair.
Should apply thermal glue to attach the heatsink to the board itself as well. Two reasons:

1. The heatsink's weight may force the solder to crack again.
2. It dissipates some heat to the board, and the board acts like a second heatsink
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Old 01-13-2017, 02:25 AM   #16
jondoe
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Default Re: LG 37LD490 - Glitching picture.

It's sitting a little high for that, but I'll see what I can do, I'd love to see the original design! I'm still waiting for the glue to turn up in the post, but the TV was left on all day yesterday watching some movies by itself and it's continues to work fine, picture wise and HDMI ports. Left off over night and back on this morning, everything good.

Feeling confident, I've ordered a replacement remote control, I'm probably tempting fate!
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Old 01-13-2017, 07:21 AM   #17
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Default Re: LG 37LD490 - Glitching picture.

I have done about 9 of these boards from LG (560 and 650 models). I have used an ATI graphics card heat sink we had in bulk (salvaged on a whim from a local school dumping old gear) that have a small flat, 5 volt fans on them. I get the 5v by regulating down 12v on the board. Initially we ran some of the 560 boards and used IR thermometers on them to see what is getting hot. It's the two processors and the two ram chips above the main processor which become too hot to touch while running.

The cheap ATI graphics card heatsink covers the main processor and the two ram chips and the air is channeled up onto the other processors heatsink.
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Old 01-13-2017, 07:36 AM   #18
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Default Re: LG 37LD490 - Glitching picture.

Quote:
Originally Posted by saddle_au View Post
I have done about 9 of these boards from LG (560 and 650 models). I have used an ATI graphics card heat sink we had in bulk (salvaged on a whim from a local school dumping old gear) that have a small flat, 5 volt fans on them. I get the 5v by regulating down 12v on the board. Initially we ran some of the 560 boards and used IR thermometers on them to see what is getting hot. It's the two processors and the two ram chips above the main processor which become too hot to touch while running.

The cheap ATI graphics card heatsink covers the main processor and the two ram chips and the air is channeled up onto the other processors heatsink.
Ive done a few bloody Lg shit got a video of me fixing one actually, most issues with Lgs is Bga solder because they failed to heatsink them XD chips properly and they run so hot. Fucking bullshit.
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Old 01-13-2017, 08:50 AM   #19
jondoe
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Default Re: LG 37LD490 - Glitching picture.

I think they are rebadged Broadcom dual core MIPS chips, 400Mhz jobs, they could really do with the extra cooling.

You could take 5v off the existing USB rail, I was considering finding a north bridge fan to screw into it.

Currently waiting for the glue to set before I screw it back up and test it some more.
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Old 01-16-2017, 01:51 AM   #20
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Default Re: LG 37LD490 - Glitching picture.

This was all going so well, until I forgot to the check the clearance of the the heat sink with the back to the tv on Unfortunately it's fouling the case, so I've had to remove it and move it up a little this would explain the odd one from factory!
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