LG 47LV550W audio and back light works / no picture

[budm]

Re: LG 47LV550W audio and back light works / no picture

OK, disconnect the those two cable and test again, if it still shows low Ohms then I would remove that and test it off the board, those readings are very low Ohms.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Will do after work, thanks.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

On a side note, I have easy access to this part:
Would it be suitable for testing the board?

[budm]

Re: LG 47LV550W audio and back light works / no picture

That should be fine, the T-CON max current is 1.26A, Inrush is 5A.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Ok transistor is now changed and voila voltages are now normal, 11,9v at TCON fuse when TV on and 0v when off. But. Picture is as you can see. First one both ribbon cables plugged and others only one.

Measured following volts at TCON, normal TV show on HDMI1:

P_VDD: 16,57v
GMA1...7: Varying 14,4v-10,5v
GMA9...18: Varying 8,6v-1,1v
VCC: 3,29v
VDD: 16,68v
VGL: -4,94v
UC1: 0v
VGH: 4,66v
VST: -4,93v
VGH_EVEN: Varying -5v-5v
VGH_F: -4,94v
GCLK1...6: Varying -3,7v-(-3,8v)
VCOM: 6,98v
Z_OUT: 8,36v
VCOMRFB: 6,97v
GIP_RST: -4,94v
VGL_1: -4,94v
VGH_ODD: Varying -5v-5v
VGH_R: 4,66v
E0: 0v
GST: 0,01v
MCLK: 0,2v
GCLK: 1,03v
VCORE: 1v
VIN: 11,84v
HVDD: 8,25v
SOE: 0,26v
VST_IN: 0,01v
OPT_N: 0v
VCOMLFB: 6,98v
PDL: 1,64v
H_CONV: 0v

What do you think, TCON or panel damage?

[budm]

Re: LG 47LV550W audio and back light works / no picture

OK, that is good to know, I wonder that may be the problem in the T-CON or the driver ICs (on the flex PCB of the LCD glsss panel).
I will let TOM66 chime in on those voltage readings on the T-CON, he knows lots more than I do about the T-CON.
By the way, good job locating that MOSFET on the board.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Thanks alot for your help, couldn't have made it this far without you.

[tibimakai]

Re: LG 47LV550W audio and back light works / no picture

In Bud's picture, at post #12 there are test points at the (far)right bottom of the T-con.
Those are the test points, that you have to measure.
Basically, they have to decrease in value, as you measure toward left.
I had on mine some test points, where I have measured 0V, which it was weird.
Write them down and post them here.

[tibimakai]

Re: LG 47LV550W audio and back light works / no picture

I still have the 42" TV and this T-con board looks very familiar, it may be the same part, maybe even the mainboard is the same.
My TV has sound, but it seems like one of the panel's tab is unbonded(lifted) from the glass.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Yeah I measured them and they are the test points GMA1...7: Varying 14,4v-10,5v
GMA9...18: Varying 8,6v-1,1v

This was with IPTV hooked. Will check without signal at some point.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

They were as you say decreasing from right to left. So does this indicate that the problem is not the TCON? I'll take a video after work but those lines change on screen when there's varying picture source.

[LGElectronics]

Re: LG 47LV550W audio and back light works / no picture

Hi Masba,
Did you try contacting LG in Finland about finding a local Authorized Service Provider or LG itself to provide you with some technical assistance for the 47LV550W?
Their number is 0800 0 LG (0800 0 54 54)...IFV

[budm]

Re: LG 47LV550W audio and back light works / no picture

You should list the GMA reading in this format:
GAM1: xxV
GMA2: xxV
.......
.......
GMA18: xxV

Vgh, Vgl, Vst_in do not look right either, hopefully TOM66 will see this thread soon.

BTW, LG is not going to do anything but trying to sell you a new TV, it will not provide service info either.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Below readings are with no input:

GMA1: 14,43v
GMA3: 14,32v
GMA4: 13,58v
GMA5: 12,50v
GMA7: 10,57v
GMA9: 8,60v
GMA10: 7,93v
GMA12: 6,21v
GMA14: 4,24v
GMA15: 3,17v
GMA18: 2,45v

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Here's a short video with no input plugged in: http://1drv.ms/1tu9SDP , I think there's some kind of "screen saver"/no input detected type of thing moving.

Also plugged computer to it and playing video makes lines move and shift the, seems like depending on how much contrast difference there is (you cant really see it properly in the video): http://1drv.ms/1sQAI88

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Here's another video where you might see abit better; http://1drv.ms/1sQE7DO

[tibimakai]

Re: LG 47LV550W audio and back light works / no picture

Those readings look good.
I personally, I would take the screen apart, at least to see the tabs, to see if anything looks bad there.
I'm thinking Windex damage(corrosion).
Only after that, I would order other boards.

[Masba]

Re: LG 47LV550W audio and back light works / no picture

Thanks for the tip, is there something special to note while taking it apart? Or better yet a step-to-step tutorial so not to do any damage?

Budm mentioned that Vgh, Vgl, Vst_in dont look normal. What would be normal voltages for those?

[Masba]

Re: LG 47LV550W audio and back light works / no picture

From what I have read in these forums it seems that problem might be low VGH voltage. Apparently it should be atleast same as VDD?

[budm]

Re: LG 47LV550W audio and back light works / no picture

See post 4 from tom:
https://www.badcaps.net/forum/showth...vgh#post489591

Tom66:
VGH = about 20 to 30V
VGL = about -5V to -10V
AVDD/VDD = about 14V to 16V

those are the key ones, all measured with chassis ground as negative."