LG 55LV5500-UA no picture or sound

[electrobe]

I have a LG 55LV5500-UA led smart tv that has no picture or sound when powered on. When the tv is turned on it powers on & the lg logo display for a couple of seconds then go off. There is no picture or sound just backlights staying on. I removed the rear cover to check for popped capacitors but there were none. I would appreciate any help.

[Hamie]

Re: LG 55LV5500-UA no picture or sound

Probably another led failure.
Upload pictures of the boards

[electrobe]

Re: LG 55LV5500-UA no picture or sound

Here are the pictures you have requested. I even took a picture of the backlights on when the power is turned on.

[Diah]

Re: LG 55LV5500-UA no picture or sound

Hamie correct, LG 55 had 2 strips, even half of one strip ligh <ou will see backlight

first check the backlight voltage one by one, which one read higher at turn on.

[budm]

Re: LG 55LV5500-UA no picture or sound

"There is no picture or sound just backlights staying on" So the backlights are actually staying ON and will go off if you turn off the power switch but you cannot see any images on the screen?
"lg logo display for a couple of seconds" LG logo on the BEZEL or actually LG image on the LCD screen?
Are you getting 12 DCV (DCV depends on the panel design) on both ends of the SMD fuse on the T-CON board?

[Diah]

Re: LG 55LV5500-UA no picture or sound

LV series of LG had in SW semi protection level. which turn off PWB off to protect other parts at main board to get damage.

[budm]

Re: LG 55LV5500-UA no picture or sound

LG EAY62169901 (EAX62876201/8) Power Supply 55LV5400 55LV5500 55LW5300 55LW5700

To OP, If you look at the LED connectors, you will see pin labels as 1A~C (4 STRINGS), 2A~C (4 STRINGS), 3B~C (4 STRINGS), and 4A~C (4 STRINGS) so you have total of 16 strings thus 16 Power MOSFETs for the 16 LED Cathodes return lines.

[electrobe]

Re: LG 55LV5500-UA no picture or sound

Yes the backlights stay on when the set is powered on & turn off when turned off. The LG logo is displayed on the screen & then disappears after a few seconds. I will check the voltages of the (16) mosfets & for 12DCV SMD fuse on the T-CON board if it has one.

[electrobe]

Re: LG 55LV5500-UA no picture or sound

Here are the voltages from the smd fuse from t-con & backlight voltages (each point being tested when powered on)

T-con smd fuse both sides 10.91 V

Starting from the lower left power ic:
1.) 12.50V at turn on then 1.6V
2.) 12.50V at turn on then 1.5V
3.) 12.50V at turn on then 1.3V
4.) 12.7V at turn on then 1.3V
5.) 12.8V at turn on then 1.3V
6.) 12.7V at turn on then 1.3V
7.) 12.3V at turn on then 1.3V
8.) 12.5V at turn on then 1.3V
9.) 12.1V at turn on then 1.1V
10.) 13V at turn on then 1.3V
11.) 12.7V at turn on then 1.1V
12.) 13V at turn on then 1.4V
13.) 12.4V at turn on then 1.2V
14.) 12.5V at turn on then 1.2V
15.) 12.4V at turn on then 1.3V
16.) 12.6V at turn on then 1.5V

[budm]

Re: LG 55LV5500-UA no picture or sound

"Starting from the lower left power ic:" Which IC is that? Do you mean the 16 Power MOSFETs? If those are what you are seeing, they are OK, as you indicated, the backlights STAY ON, if there was an error the backlights will be commanded to turn OFF ALL the LEDs.

[electrobe]

Re: LG 55LV5500-UA no picture or sound

Yes the (16) power mosfets

[budm]

Re: LG 55LV5500-UA no picture or sound

So you do have Voltage to the T-CON that means the main board did not go into standby mode otherwise the DCV for the T-CON will not be there and the backlights also stay on, but you have no image on the screen so either the main board stops sending the signals to T-CON or something is going on with T-CON.
Try having one ribbon cables between the T-CON and the LCD panel connected one at time to see what you get.

[electrobe]

Re: LG 55LV5500-UA no picture or sound

I disconnected each ribbon cable going to the screen & nothing was displayed. The backlights stayed on & now the LG logo no longer shows on the set when turned on.

[budm]

Re: LG 55LV5500-UA no picture or sound

Make sure the ribbon cables are properly seated back in place.

[electrobe]

Re: LG 55LV5500-UA no picture or sound

I went back & made sure the ribbon cables were properly seated & still no LG logo displayed on the screen. The backlights stay on but that is it.

[Diah]

Re: LG 55LV5500-UA no picture or sound

I went back & made sure the ribbon cables were properly seated & still no LG logo displayed on the screen. The backlights stay on but that is it.

regarding to the age of the TV and environment, the Gold print on ribbon cables became very sensitive at take out and reset, check them with magnifier after you had back LG Logo take it in parts and follow post no 2.

[comptek]

Re: LG 55LV5500-UA no picture or sound

Does Menu show up ?

[electrobe]

Re: LG 55LV5500-UA no picture or sound

I will check the ribbon cable pins under magnification & will report back. The menu doesn't show either. I did find one possible cause though when I was searching the back of the main input board. I found a burned 3-pin chip with the markings (X75A) with (16) written under it. I will upload a picture of it tomorrow.

[electrobe]

Re: LG 55LV5500-UA no picture or sound

Here is a picture of the burned chip. I do not know what it is yet from the markings I previous stated.

[electrobe]

Re: LG 55LV5500-UA no picture or sound

I found out the part is a "P-Channel Enhancement Mode Field Effect Transistor" & is located in the "panel power" section on the main board. I do not have one of these on hand to replace to see what will happen.