LG 47G2 LCD - has backlight, but no video

[SurrealMustard]

I've been working on this LG 47G2 LCD television that powers up and lights up the backlight, but doesn't actually put anything on the screen. I have tried replacing the T CON board already, but it still does the same thing.

Any ideas?

[Hamie]

Re: LG 47G2 LCD - has backlight, but no video

Upload some photos.

Also you should get 12v going to the tcon, check both ends of the pico fuse to ensure that 12v is present.

If you've bought a tcon from eBay then it's certainly not guaranteed to be working

[infringer]

Re: LG 47G2 LCD - has backlight, but no video

Indeed hamie is correct not everything from ebay works often people pull parts out of a working TV with a smashed screen or something just because components were working before the smashed screen doesn't mean it will work after but it is not unlikely that it is as it is cheaper to estimate that something will be working given the conditions rather than actually set it up and test everything.

hrmmm if the TCon was replaced did you make sure all LVDS ribbons are plugged in on both sides and well. Did you also verify and unplug and replug all connections to be sure you are getting good connections everywhere. Even if a wire looks plugged in once in a while it is this simple action that will fix your problem at times. If this all checks out then start digging a bit deeper seeing as you have all your power on check your video sources press the menu button see if this comes up. If this does not come up then proceed to diagnosing further. Which in your case it doesn't sound like you have anything but a backlight I would hate to say it is your video board and be wrong but it did happen with me on a xvt42 vizio so I wound up replacing both. Obviously their is more that one way to skin the cat but just my non expert 2 cents.

[SurrealMustard]

Details and pictures

Upload some photos.

Also you should get 12v going to the tcon, check both ends of the pico fuse to ensure that 12v is present.

If you've bought a tcon from eBay then it's certainly not guaranteed to be working

Okay. I have attached some photos of the boards to this post and double checked the fuse on the T CON; it appears to be okay on both the original and replacement units. As far as checking for power on the T CON goes, is there any good points on there to test that? The pins on that connector look really close together and easy to accidentally short out.

Indeed hamie is correct not everything from ebay works often people pull parts out of a working TV with a smashed screen or something just because components were working before the smashed screen doesn't mean it will work after but it is not unlikely that it is as it is cheaper to estimate that something will be working given the conditions rather than actually set it up and test everything.

hrmmm if the TCon was replaced did you make sure all LVDS ribbons are plugged in on both sides and well. Did you also verify and unplug and replug all connections to be sure you are getting good connections everywhere. Even if a wire looks plugged in once in a while it is this simple action that will fix your problem at times. If this all checks out then start digging a bit deeper seeing as you have all your power on check your video sources press the menu button see if this comes up. If this does not come up then proceed to diagnosing further. Which in your case it doesn't sound like you have anything but a backlight I would hate to say it is your video board and be wrong but it did happen with me on a xvt42 vizio so I wound up replacing both. Obviously their is more that one way to skin the cat but just my non expert 2 cents.

Looks like your post came in after I clicked reply and before I clicked submit on my original message. I did end up double checking to make sure the ribbon cables were in tight on the T CON, but I'm still getting the same thing. The set responds to the power button, but I don't get any feedback on screen when pressing any other button. There is supposedly sound, but I don't know what input it's on, so I can't test that for sure.

[infringer]

Re: LG 47G2 LCD - has backlight, but no video

you should never connect or disconnect these cables while the tv is plugged in or powered on in any way yes this would be a good way to short something out. Although I've done it forgetting that it was plugged in a reconnected my bluray drive ribbon and it touched two pins incorrectly when trying to get it to seat correctly I'm sure the same could happen in your case as well.

[Hamie]

Re: LG 47G2 LCD - has backlight, but no video

Need to check the fuse and make sure it's getting 12v

You shouldn't be in danger of shorting anything out.

Put black probe on chassis (ground)

Then red probe to one first end of the fuse.
Then change to the other side and check the other end.

You should get 12 volts going in, and 12v going out the fuse.

If you don't get 12v going in, suspect mainboard or LVDS cable.

If you get 12v going in but nothing going out, bad tcon.

[SurrealMustard]

The Plot thickens

Need to check the fuse and make sure it's getting 12v

You shouldn't be in danger of shorting anything out.

Put black probe on chassis (ground)

Then red probe to one first end of the fuse.
Then change to the other side and check the other end.

You should get 12 volts going in, and 12v going out the fuse.

If you don't get 12v going in, suspect mainboard or LVDS cable.

If you get 12v going in but nothing going out, bad tcon.

The plot thickens.

With the new T CON, I'm getting voltage on the bottom of the fuse while the set is running, no voltage on the top of the fuse. With the old T CON, I'm getting voltage on both sides of the fuse, which is how it should be. I know I didn't get them mixed up, in case you were wondering .

[Hamie]

Re: LG 47G2 LCD - has backlight, but no video

interesting.

With your original tcon in the set.
Unhook one half of the tcon ribbons. and power up the TV.

See if you get half and image on the screen, if not reverse the process and unhook the other one, and see if you get half an image on the other side of the screen.

Unfotunatley if you do get half image one either side you have a bad panel.

[Hamie]

Re: LG 47G2 LCD - has backlight, but no video

Also when getting a refund for your tcon board you should demand a full refund, if they want it returned say ok but you want your postage refunded aswel.
Sending someone a board that has a open fuse is practically criminal. :-)

[SurrealMustard]

I'll report back with my findings.

interesting.

With your original tcon in the set.
Unhook one half of the tcon ribbons. and power up the TV.

See if you get half and image on the screen, if not reverse the process and unhook the other one, and see if you get half an image on the other side of the screen.

Unfotunatley if you do get half image one either side you have a bad panel.

I will do that when I'm in next and report the results back.

Also when getting a refund for your tcon board you should demand a full refund, if they want it returned say ok but you want your postage refunded aswel.
Sending someone a board that has a open fuse is practically criminal. :-)

The fuse wasn't open, but it's still good advice. Most eBay sellers are pretty good about that stuff though (that said, I did once buy a power supply board for a different television from a site called "Electron Resort"; not only was the part defective, but they wanted me to diagnose it, pay return shipping, and pay a restocking fee).

[SurrealMustard]

Findings

interesting.

With your original tcon in the set.
Unhook one half of the tcon ribbons. and power up the TV.

See if you get half and image on the screen, if not reverse the process and unhook the other one, and see if you get half an image on the other side of the screen.

Unfotunatley if you do get half image one either side you have a bad panel.

With the left ribbon unplugged, I'm getting vertical bars on the left side of the screen, solid gray on the right. With the right ribbon unplugged, I'm getting nothing on screen, but I'll check this a bit more thoroughly when I can move this thing to a position where I can see the screen more easily while the unit is face down.

[SurrealMustard]

Follow-up and picture

Further testing revealed little more than what was discovered earlier. With the left ribbon connected and the right ribbon disconnected, I'm getting nothing at all. With the right ribbon connected and the left ribbon disconnected, I'm getting what is seen in the picture.

Am I looking at a bad panel here or should I try another T Con board (or something else altogether)?

[Th3_uN1Qu3]

Re: LG 47G2 LCD - has backlight, but no video

That still looks like a T-Con fault to me, it is not unlikely that you have two bad T-Cons. I'd say the panel is most likely okay.

[SurrealMustard]

Still nothing

Installed a new T Con, getting the exact same symptoms as before. Fuse is good and proper voltage is present on both sides. Any ideas?

[SurrealMustard]

Anyone? Anything?

Nothing? Is it possible that the panel is just bad?

[superg]

Re: LG 47G2 LCD - has backlight, but no video

Did you try replacing the LVDS cable? Was recently working on some LGs @ a hotel. One had a bad t-con which when I replaced gave me a solarised image which remained even though I replaced the t-con again.I then replaced the LVDS cable and viola, problem solved.

[SurrealMustard]

Cables

Did you try replacing the LVDS cable? Was recently working on some LGs @ a hotel. One had a bad t-con which when I replaced gave me a solarised image which remained even though I replaced the t-con again.I then replaced the LVDS cable and viola, problem solved.

Would that be the one going from the mainboard to the T Con or the ones going from the T Con to the panel?

[vinceroger69]

Re: LG 47G2 LCD - has backlight, but no video

lvds is mainboard to the T Con.

[SurrealMustard]

Ribbon

lvds is mainboard to the T Con.

I'll see about ordering one and report back with the results.

[newtothis]

Re: LG 47G2 LCD - has backlight, but no video

The lines on screen one sided says panel fault to me