LG55LS4500 picture went bye bye

[Tim K]

LG55LS4500 picture started displaying dark horizontal lines (alternate picture lines were basically black). Then the next day no picture at all. Now there is basically no picture except for some vertical light gray bands that seem to move across the screen. I opened up the TV and saw no fried caps or any obvious failures. Last year (about 18mo ago) this TV POPPED and went black. I opened it up and found a fried cap. I replaced it and everything was good. This time there is no obvious cause. Backlight works fine. I checked and reset all the ribbons. Nothing. See attached photos. I'd like to fix this TV as it's not that old and it is just used for my kids to play xbox.

Thanks,

[budm]

Re: LG55LS4500 picture went bye bye

We need to see the pictures of the whole backside of the TV showing all the boards.
Does it have stand alone T-CON board? If it does, what do you get on the screen if you have only one ribbon cable between the T-CON and the LCD panel connected one at at time?

[Tim K]

Re: LG55LS4500 picture went bye bye

We need to see the pictures of the whole backside of the TV showing all the boards.
Does it have stand alone T-CON board? If it does, what do you get on the screen if you have only one ribbon cable between the T-CON and the LCD panel connected one at at time?

Here is the back panel. I assume you are referring to the two ribbons at the top...the one with the black connector and the one with the white. If BOTH are connected, I get the mostly black screen with the vertical white/grey patches that change location over time. If I disconnect either ribbon, I see the same thing for a second, then it all goes dark and a yellow LED starts flashing on the right side of that orange main board.

Thanks,

Tim

[budm]

Re: LG55LS4500 picture went bye bye

Your T-CON board is under the metal shileld at the bottom center of the TV, you see white flat cable with blue marking.
Those two cables you pulled ARE NOT cables for T-CON, those are for LED backlights, make sure you put them back on correctly.

[Tim K]

Re: LG55LS4500 picture went bye bye

When I disconnect the white ribbons with the blue tape from the T-con and turn it on, the backlight works but the screen is blank. When the cable is connected to the t-con, the screen gets that grey/white vertical band that moves left to right across the screen (it changes position every couple of seconds).

Is this a bad T-con, and if so does it need to be replaced or are there parts available cheaper?

[budm]

Re: LG55LS4500 picture went bye bye

That is not the cable (between T-CON and the Main board) I want you to disconnect, there are two ribbon cables between the TCON and the LCD panel that you need to have one ribbon cable connected one at a time.
Did you remove the metal shield to get to the T-CON board.
Pictures of the T-CON?

[nomoresonys]

Re: LG55LS4500 picture went bye bye

Are you disconnecting both ribbons at the same time? You need to unplug tv, take out one ribbon, plug tv back in try it then do the same other side. (best practice is don't unplug any cables while tv is plugged in) so you unplug tv before disconnecting cable.

[Tim K]

Re: LG55LS4500 picture went bye bye

OK. I didn't see the two cables at the bottom before.

[yes, I always unplug the TV before doing anything inside it]

I disconnected one, powered up....checked the screen. right side is white, left side is black with vertical lines. unplugged. reconnected the first, disconnected the other, powered up...checked the screen. left side is white, right side is black with vertical lines.

[Diah]

Re: LG55LS4500 picture went bye bye

i remember on this forum was some one from UK had same issue and it was BGA at main board which he backed his MB and it worked perfectly

[Tim K]

Re: LG55LS4500 picture went bye bye

I read some of those threads. I tried heating the back of the chip on the MB but that had no impact. Looking for other suggestions. If I need to replace a board and its cheap enough I'll just do that.

[budm]

Re: LG55LS4500 picture went bye bye

Please up load good clear straight shot pictures of the T-CON board so I can locate the Voltage test points.

[Tim K]

Re: LG55LS4500 picture went bye bye

Please up load good clear straight shot pictures of the T-CON board so I can locate the Voltage test points.

Here you go. Hope it's clear enough.

[budm]

Re: LG55LS4500 picture went bye bye

The test points that I can see so far are
HVDD
VDD
VGL
VGH
VIN
Vcore
VCC
VCC18

[Tim K]

Re: LG55LS4500 picture went bye bye

The test points that I can see so far are
HVDD
VDD
VGL
VGH
VIN
Vcore
VCC
VCC18

Here are some more shots. Hopefully a little clearer.

[budm]

Re: LG55LS4500 picture went bye bye

Just check those test points and report them.

[Tim K]

Re: LG55LS4500 picture went bye bye

Just check those test points and report them.

Can you confirm I have the points right? Some of them are unclear which points they are indicating. See below drawing. If I have any of them wrong please let me know.

Thanks again.

Tim

[Tim K]

Re: LG55LS4500 picture went bye bye

HVDD, VIN and VCC are particularly unclear to me.

[budm]

Re: LG55LS4500 picture went bye bye

You got it right. The bare copper dots are the test points, so you have it on the leg of the component which you can see that it goes to each bare copper dot.

[Tim K]

Re: LG55LS4500 picture went bye bye

Here are the voltages. Sadly, at 45 I had to find a magnifying glass to see what I was doing....

HVDD: 5.79
VDD: 11.56
VGL: 6.85
VGH: 0.77
VIN: 11.79
Vcore: 1.78
VCC: 3.25
VCC18: 1.78

[budm]

Re: LG55LS4500 picture went bye bye

1) Check the reistance between VGH and Ground to see what you get.
2) Disconnect the cables between T-CON and the LCD panel and see what VGH will be.
BTW, VGL is the LCD minus power supply so it should show as minus reading on your meter, I.E. -6.85V.
Here is some info about LCD Bias power supply function: