LG 47LV3700 No Picture, Sound Ok, Backlight Ok

[yegoshin]

Hey guys I need a little bit of help.

I got an LG 47LV3700, the picture went out the other day. It was playing netflix the sound continued the backlight was on. Turning it [TV] off for a while seemed to solve it the problem temporarily (worked for a 2-10mins afterwards), then it happened again a few times and now its just blank.

There are a few thin lines up at the top of the screen and they seem to change with the signal.
Sound Good
Backlight Good
Picture - Mostly blank, sometimes thin lines up top. (Once it lit up grey in the middle of the screen like a circle of light or something slowly and then faded)

Anyone have any thoughts on this? I attached pictures of the boards inside etc...

I checked the fuse on the Tcon its 12v on ether side and its good
Unplugging ether side of the Tcon results in white being displayed on that side of the screen.

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Bump? anyone? Bueller?

[budm]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

If you look at the T-CON board, there are many test points that have labels for them, for examples:
VGH, VGL, VCOM , GMA1~18, etc. So check and see if they are dead or not.

[ozzy214]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

If tcon is cheap enough, shot gun. In my experience it is tcon or panel issue. Last is main board when you got a black screen with some lines running vertical...Have a vizio here doing the same thing that I wanted to fix for my gf house and doing the same damn thing. Actualy a common failure with this vizio im working on...hard to find a tcon under 60 bucks.

[budm]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

LG 6871L-2605A (6870C-0368A)
SJ has the 'B' version but not in stock:
http://www.shopjimmy.com/lg-6871l-2605b-t-con-board.htm

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Thank you for the reply's.

If you look at the T-CON board, there are many test points that have labels for them, for examples:
VGH, VGL, VCOM , GMA1~18, etc. So check and see if they are dead or not.

At the time the TV was open (had to hand it back on the wall for storage). I measured those and got voltages on those. Though I didn't write those down

If tcon is cheap enough, shot gun. In my experience it is tcon or panel issue. Last is main board when you got a black screen with some lines running vertical...

My lines are running horizontally

LG 6871L-2605A (6870C-0368A)
SJ has the 'B' version but not in stock:
http://www.shopjimmy.com/lg-6871l-2605b-t-con-board.htm

I shotgunned this one:
http://www.aliexpress.com/store/prod...618118946.html

It has an extra connector & resistors stuffed in, do you think it will matter?
Lets hope China Post gets it here quick.

Thank you guys for the reply. I'll keep you updated when the T-Con comes in and I'll open up the TV again an measure all those voltages exactly. Can I safely stick the new T-con board in without fear of burning something?

Did anyone want a youtube of what the screen looks like right now? Will that help in diagnosing it?

[fzabkar]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Service manuals:
http://elektrotanya.com/?q=showresul...at2=schematics

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Ok the new T-con board didn't fix it.
Here are the voltages off the test points:
VDD 16.32
VCC 3.27
VIN 11.94
HVDD 7.85
VCORE 1.79

VGL -4.96
VGH 26.7

VCOM 6.99
VCMORFB 6.98
GID_RST -4.94
VGL_1 -4.96
VGH_ODD -4.96
VGH_R 26.7
GCLK5 -4.8 (DROPPING TO 0)
GCLK3 -4.96
GCLK1 -4.96

VST 26.7
VGH_EVEN 26.7 (DROPPING TO -4.9 THEN BACK)
VGH_F -4.96
GCLK6 -4.8 (DROPPING TO 0)
GCLK4 -4.9 (DROPPING TO 0)
GCLK2 -4.8 (DROPPING TO 0)

Z_OUT 0

VCOMLFB 6.98
SOE 0.41
VST_IN 4.4mV
OPT_IN 1.4mV

P_VDD 16.32

GMA1 4.0mV
GMA3 13.65
GMA4 12.98
GMA5 11.86
GMA7 10.28
GMA9 5.3mV
GMA10 7.1mV
GMA12 6.29
GMA14 4.19
GMA15 3.38
GMA16 2.75
GMA18 5.0mV
H_CONV 1.5mV
POL 1.64

GCLK 1.72
MCLK 1.25
GST 7.7mV
EO 1.4mV

Anyone have anything else I could try?

[vinceroger69]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

looks like a faulty tcon to me judging by the gamma voltages maybe run the same test with your old tcon too

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Old T-con Reading in Black NEW T-Con in Red
VDD 16.32 16.63
VCC 3.27 3.29
VIN 11.94 11.98
HVDD 7.85 8.25
VCORE 1.79 1.79

VGL -4.96 -5.00
VGH 26.7 27.7

VCOM 6.99 7.34
VCMORFB 6.98 7.33
GID_RST -4.94 -5.00
VGL_1 -4.96 -5.00
VGH_ODD -4.96 27.7 (dropping to -5.00)
VGH_R 26.7 27.7
GCLK5 -4.8 (DROPPING TO 0) -4.5
GCLK3 -4.96 -4.3
GCLK1 -4.96 -4.4

VST 26.7 -4.7 (dropping to 0)
VGH_EVEN 26.7 (DROPPING TO -4.9 THEN BACK) 27.7 (Dropping to -5 then back to 27.7)
VGH_F -4.96 -5
GCLK6 -4.8 (DROPPING TO 0) -4.5
GCLK4 -4.9 (DROPPING TO 0) -4.5
GCLK2 -4.8 (DROPPING TO 0) -4.5

Z_OUT 0 0

VCOMLFB 6.98 7.3
SOE 0.41 0.4
VST_IN 4.4mV 4.4mV
OPT_IN 1.4mV 1.1mV

P_VDD 16.32 16.62

GMA1 4.0mV 0.7mV
GMA3 13.65 14.28
GMA4 12.98 13.5
GMA5 11.86 12.5
GMA7 10.28 10.6
GMA9 5.3mV 1.0mV
GMA10 7.1mV 0.9mV
GMA12 6.29 6.21
GMA14 4.19 4.27
GMA15 3.38 3.19
GMA16 2.75 2.49
GMA18 5.0mV 1.1mV
H_CONV 1.5mV 3.3 (dropping to 0 then back to 3.3)
POL 1.64 1.6 (unstable)

GCLK 1.72 same
MCLK 1.25 same
GST 7.7mV same
EO 1.4mV same

Power Board Connectors to main board
Reverse 7.0mV
NV 0
SCLK 3.3mV
GND -5mV
SIN -6mV
SCL 3.19
SDA 3.22
VSYNC -8mV

NC
12V 11.97
12V 11.96
12V 11.97
GND
GND
3.5V 3.5
3.5V 3.5
GND
GND
24V 24.2
PWR-ON 3.4
ERROR
PWM -1.45
NC
DRY-ON 3.23 (dropping 2.8)
VSYNC 20mV (unstable)
GND
3.5V 3.49
3.5V 3.49
GND
GND
24V 24.2
24V 24.2

[budm]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

'VGH_EVEN 26.7 (DROPPING TO -4.9 THEN BACK) 27.7 (Dropping to -5 then back to 27.7)'
That look like you may have bad driver ICs (they are on the flexible PCB between the Glass panel and the rigid tab bonding PCB) on the LCD panel,
Disconnect the cables between the T-CON and the LCD panel to see if the Voltage will be stable.

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Disconnect the cables between the T-CON and the LCD panel to see if the Voltage will be stable.

I measured all the voltages with the T-con disconnected from the LCD (2 ribbon cables)

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Here is the current behavior with the old T-Con (new on is similar):
https://www.youtube.com/watch?v=ltItM_wiMFw

Any suggestions on what else to check? Where to go from here?

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Bump. Anyone got any suggestions to check anything else?

[spintop]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

is that a LED driver on the top left covered by the white sticker in your first photo ?
maybe u can check that the power and fuse are ok.
if not, probably u can change the main board.

I have a rather similar LG 42LV3730 model, i changed the mainboard. mine issue cannot boot up only show LG logo and hang.

LG led tv has lots of main board issues, if u google, people use baking methods. probably weak joints in the BGA chips - video, flash, dram, static ram

[yegoshin]

Re: LG 47LV3700 No Picture, Sound Ok, Backlight Ok

Just FYI I was able to revive this (47LV3700) and another LG 47LV5500 (after trying every possible part swap between them) by baking the motherboards (OG trick from bad solder joints on Nvidia cards )

Now if only the smart portion of these TV's actually continued functioning:



Out of these only [Vudu, Cinema Now, MLB, Netflix, Napster] are left. Playing to Youtube app off my phone is no longer an option since June 2017
Now I get it that older tech from 2012 losing support is inevitable however pretty sure all of my PC's (even if I dig out ones with XP) with HDMI out still work with ANY of multiple streaming services and new ones too. Just keep that in mind when making your next purchase decision based on bells and whistles hung on there by TV manufacturers like LG, Samsung, Sony etc...