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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
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Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G


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


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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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PostLink    Posted: Sat Apr 25, 2015 7:16 pm    Post subject: Reply with quote

Anyone?
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AnalogRocks
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TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Sat Apr 25, 2015 7:54 pm    Post subject: Reply with quote

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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TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Sat Apr 25, 2015 8:46 pm    Post subject: Reply with quote

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




Joined: 09 Oct 2013
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TV/Projector: BD808s, BG1209/2


PostLink    Posted: Sun Apr 26, 2015 7:12 pm    Post subject: Reply with quote

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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PostLink    Posted: Mon Apr 27, 2015 2:25 pm    Post subject: Reply with quote

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




Joined: 09 Oct 2013
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PostLink    Posted: Mon Apr 27, 2015 2:28 pm    Post subject: Reply with quote

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

TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Mon Apr 27, 2015 5:02 pm    Post subject: Reply with quote

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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PostLink    Posted: Mon Apr 27, 2015 5:03 pm    Post subject: Reply with quote

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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PostLink    Posted: Wed Apr 29, 2015 9:18 pm    Post subject: Reply with quote

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?

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Curt Palme
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PostLink    Posted: Wed Apr 29, 2015 9:26 pm    Post subject: Reply with quote

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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PostLink    Posted: Wed Apr 29, 2015 9:42 pm    Post subject: Reply with quote

Here they are. Slightly different numbers. The eBay part is newer:
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Curt Palme
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PostLink    Posted: Wed Apr 29, 2015 10:02 pm    Post subject: Reply with quote

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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PostLink    Posted: Thu Apr 30, 2015 4:34 pm    Post subject: Reply with quote

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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PostLink    Posted: Sat May 30, 2015 7:35 pm    Post subject: Reply with quote

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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PostLink    Posted: Fri Jun 12, 2015 2:48 am    Post subject: Reply with quote

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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PostLink    Posted: Wed Jul 22, 2015 8:00 pm    Post subject: Reply with quote

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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PostLink    Posted: Sun Aug 30, 2015 6:29 pm    Post subject: Reply with quote

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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PostLink    Posted: Sun Aug 30, 2015 9:36 pm    Post subject: Reply with quote

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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PostLink    Posted: Tue Sep 01, 2015 6:33 am    Post subject: Reply with quote

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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