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LG M4715CG / M4715CCBA back lite but no picture
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AnalogRocks
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Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G

Posted: Thu Apr 23, 2015 5:42 pm    Post subject: LG M4715CG / M4715CCBA back lite but no picture

Hello all. Found one of these LCD industrial monitors. Ran the PC into it, PC sent 1080p, screen backlight is on just the ocasional flickering across the top of the screen then the middle of the screen.

I have it open,

Any common areas to look at?

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AnalogRocks
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Posted: Sat Apr 25, 2015 7:16 pm    Post subject:

Anyone?
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AnalogRocks
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Posted: Sat Apr 25, 2015 7:54 pm    Post subject:

Got a picture via S-video. Full screen sttic but that's more then what VGA gave me.

It actually went clear for a second too!
There's a 6" wide bright bar on the right side of the screen about 10" out too. Video is displayed but it's a brighter band. Stationary, not rolling like hum bars, and vertical not horizontal.

Just noticed the picture within the band is color inverted (negative) and shifted down by 1/4 inch

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AnalogRocks
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Posted: Sat Apr 25, 2015 8:46 pm    Post subject:

And now the right half of the screen is blank...
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winny



Joined: 09 Oct 2013
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Location: Sweden

TV/Projector: BD808s, BG1209/2

Posted: Sun Apr 26, 2015 7:12 pm    Post subject:

Store it until you can find another one identical, swap the hopefully working video boards/LCD-drivers from it and have one working? Service manual? Toss it?
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Curt Palme
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Posted: Mon Apr 27, 2015 2:25 pm    Post subject:

Bad T con board or bad system board would be my guess.
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winny



Joined: 09 Oct 2013
Posts: 403
Location: Sweden

TV/Projector: BD808s, BG1209/2

Posted: Mon Apr 27, 2015 2:28 pm    Post subject:

Remelt all solder joints in the oven? Nothing to loose?

http://hardforum.com/showpost.php?p=1035104340&postcount=648

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AnalogRocks
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Location: Toronto, Ontario, Canada

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Posted: Mon Apr 27, 2015 5:02 pm    Post subject:

winny wrote:
Remelt all solder joints in the oven? Nothing to loose?

http://hardforum.com/showpost.php?p=1035104340&postcount=648


Interesting! Tha sure saves time soldering!

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AnalogRocks
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Posted: Mon Apr 27, 2015 5:03 pm    Post subject:

Curt Palme wrote:
Bad T con board or bad system board would be my guess.


Any way to test, or do I just start replacing boards?

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AnalogRocks
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Posted: Wed Apr 29, 2015 9:18 pm    Post subject:

Found the T-CON board on ebay: LG M4715CG CONTROL BOARD 6870C-0364B
http://www.ebay.com/itm/LG-M4715CG-CONTROL-BOARD-6870C-0364B-/171291116225?pt=LH_DefaultDomain_0&hash=item27e1bf02c1

Mine is an older version, slightly different layout. BUT it says from the same model TV. Do you think it will work?



900_57.JPG
 Description:
eBay Part
 Filesize:  148.68 KB
 Viewed:  117 Time(s)

900_57.JPG



900_IMG_0931.JPG
 Description:
My current board
 Filesize:  287.62 KB
 Viewed:  117 Time(s)

900_IMG_0931.JPG



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Curt Palme
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Posted: Wed Apr 29, 2015 9:26 pm    Post subject:

It's possible, but it's common for production runs to change, so all you can do is try it. Did you check the 2 amp SMT fuse on the orignal board? Those can blow open for no reason, giving the exact symptom you describe.

<edit> never mind on the fuse, you did get a pix with Svideo. Not the fuse.

If the small print part numbers match up, you're OK. if not, they won't work.
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AnalogRocks
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Posted: Wed Apr 29, 2015 9:42 pm    Post subject:

Here they are. Slightly different numbers. The eBay part is newer:


part_number_eBay_57.JPG
 Description:
eBay part number
 Filesize:  10.66 KB
 Viewed:  109 Time(s)

part_number_eBay_57.JPG



Part_Number_IMG_0932.JPG
 Description:
47" Monitor current part number
 Filesize:  86.31 KB
 Viewed:  109 Time(s)

Part_Number_IMG_0932.JPG



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Curt Palme
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Posted: Wed Apr 29, 2015 10:02 pm    Post subject:

I'll bet they won't work. Made that mistake a few times. You'll probably get a pix, but it may have lines, be pixellated, etc.
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AnalogRocks
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Posted: Thu Apr 30, 2015 4:34 pm    Post subject:

Another one just showed up with the right part number for $16.50 and free shipping. Time to roll the bones...

http://www.ebay.com/itm/121520703977

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AnalogRocks
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Posted: Sat May 30, 2015 7:35 pm    Post subject:

Tried this but no go. Still have the screen band and the right half of the screen is blank. Maybe one of the LCD driver boards or input board?

I can't even get a picture with s-video now.

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AnalogRocks
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Posted: Fri Jun 12, 2015 2:48 am    Post subject:

AnalogRocks wrote:
Tried this but no go. Still have the screen band and the right half of the screen is blank. Maybe one of the LCD driver boards or input board?

I can't even get a picture with s-video now.


On these LCD's are there separate boards for the left and right sides of the screen?

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AnalogRocks
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Posted: Wed Jul 22, 2015 8:00 pm    Post subject:

Which Caigs Deoxit version should I order to clean this TV? It has an intermittent connection and was left out in the rain making for some dirty connections.
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AnalogRocks
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Posted: Sun Aug 30, 2015 6:29 pm    Post subject:

Tried the new T-con board, got no picture. I have it open and I'll be cleaning things with Caig's. I may just swap back to the other board to see if I can get it to go.
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Jeremy112



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Posted: Sun Aug 30, 2015 9:36 pm    Post subject:

You have to remember with LCD displays that the possibility exists that the LCD panel itself is toast. The only boards directly on the LCD panel are likely a couple PCBs that the T-CON board connects to, those could very likely have failed.
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AnalogRocks
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Posted: Tue Sep 01, 2015 6:33 am    Post subject:

I had a picture with this one via S-video. I think the input board may be fugged.

I cleaned all the contacts with Caigs. The power and back light will stay on now. So one step closer Thumbs Up

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