I have a Vizio E601i-A3 LCD TV. One morning when I turned it on, I heard sound (coming through the optical audio out port) but could not see video. However, when I shined a flashlight on the screen, I could see that the LCD panel was working, indicating that the LED backlighting had failed. I tore the TV apart to the point where I can access the two strips of LEDs that run along the bottom of the TV (this TV is edge-lit). The LED strips each have 68 LEDs (identified as 4 sets of 17 LEDs), which appear to be "LG Innotek 7030PKG LEDs".

I am trying to figure out how to test to see if they are working as expected, or determine what might have caused them to fail. I was able to find an LG brochure that includes an entry for a "7030 series" that looks the same. The information in the brochure indicates a forward voltage range of 2.8 to 3.2 volts, a forward current of 200 mA with a maximum current of 280 mA. I am not 100% sure this is what I have, but it probably is.

None of the 136 individual LEDs light up at 3 volts However, all of them begin to light up and show current at around 4.5 volts, and they continue to get brighter through 5.0 volts (I have not pushed the voltage higher to prevent damaging them, although that is probably a moot point at this stage). However, the current never seems to even reach 1 mA (more like 0.4 mA), and the LEDs do not get very bright. Also, I can light a pair of adjacent LEDs at 10 volts, three adjacent LEDs at 15 volts, and so on, up to six adjacent LEDs at 30 volts (as long as I stay within the groups of 17 LEDs). However, with the voltage any lower, they do not light.

I have seen many postings on the Internet showing strips of LEDs in which a few individual LEDs are either very dim or completely burnt out, but I have never seen anything like my case where none of them light up with the rated voltage, but all of them light up at a slightly higher voltage. It seems like the morning we turned on the TV and saw no backlight (after everything was fine the night before), all 136 LEDs simultaneously short-circuited to an extent that they still work dimly at the slightly higher voltage.

I posted a lot more details on a forum called BadCaps. Does anybody know a good way to test my LEDs, or does the information I have already posted make it clear that they are all damaged? Also, I am trying to figure out whether the problem is with the LED strips, the power supply board, or both (e.g., did a problem with the power supply board damage all of them such that I should replace all of these items or risk burning out another set of LED strips).

 

i suspect the LED driver is at fault rather than the LEDs themselves. Some LEDs on the market contain 2 die these days giving it a 6.6V rating at half the 3.3V operating current. I think this is what your looking at. You could try setting the current to 1 or 2mA and turn up the volts slowly. If an LED is dead it won't illuminate full stop.

 

Definitely the portion of the system to check is the driver circuit, because the LEDs are in multiple strings, and so if some had failed others would probably still be lighting. AND, based on what I have heard about repairing the driver circuits, usually the parts that fail are some of the larger capacitors, since they are fairly highly stressed components in switching power supplies. Checking the voltage at the LED strip terminals should be one of the first steps in your diagnostic process.

 

Thanks Marc Sugrue and MisterBill2. I was reluctant to turn up the voltage past 5.0 volts, because so many people had told me these LEDs should work at 3.0 volts. And, even though the LED "chips" look like they are pairs, the LG brochure suggested that they (7030 series?) should operate at 2.8 to 3.2 volts. However, I turned up the voltage, and very soon on the way up to 6.0 volts, the LEDs became extremely bright, and they appeared to draw about 35 mA at that voltage. And every single one of the 136 LEDs worked fine. I wore sunglasses while testing, but they still hurt my eyes.

Strangely enough, after reassembling the TV to the point where I could power it up, the backlighting was working fine again after power up. I am wondering whether there was some physical issue that I might have (at least temporarily) corrected while fiddling with and testing all of the LEDs. Hopefully, they will not fail again during more intense usage.

Unfortunately, I now see strange vertical lines on the screen after fully re-assembling the TV, so I guess I messed something else up while "fixing" the backlight issue. These are not the static vertical lines that I see in many troubleshooting posts. They are more dynamic in nature--dancing around with objects in the image based on the color. So, I have to figure out what is going one, such as a loose connection, a bad main board, a bad T-CON board...or maybe it is time to give up on this TV.

 

I would first examine the installation of shielding materials that you may not have correctly re-attached, since shielding is used to prevent that sort of thing.

 

I would first examine the installation of shielding materials that you may not have correctly re-attached, since shielding is used to prevent that sort of thing.

I re-seated the ribbon cables and re-routed the speaker cable away from the ribbon connectors--and I also did not tighten the screws of the back panel as tightly. Now, my TV seems to be working OK again! If anybody happens across this thread in the future and is curious about the details, I have posted more on the BadCaps forum. Thanks for everybody's help.

 

I re-seated the ribbon cables and re-routed the speaker cable away from the ribbon connectors--and I also did not tighten the screws of the back panel as tightly. Now, my TV seems to be working OK again! If anybody happens across this thread in the future and is curious about the details, I have posted more on the BadCaps forum. Thanks for everybody's help.

So are the lines gone now? I am quite aware that sometimes problems just mysteriously go away when all we do is touch things. It is seldom actual magic, but who really knows?

 

Yeah, the lines disappeared. I just don't know whether it was the re-seating of the ribbon cable connectors (probably), the re-routing of the speaker wire (it was originally routed next to two of the ribbon cable connectors, so I doubt moving that made a difference), or just taking the back off and putting it back on a bit looser (almost certainly did not make a difference, but possibly). The backlight LEDs also just started working again after fiddling with them, so the whole incident was a bunch of voodoo, and I am not really expecting the fix to last.