Vizio E470i-AO - Backlight LED Problem

[grimacelord]

Re: Vizio E470i-AO - Backlight LED Problem

...
I have a feeling one or more LED strip has open circuit...

Thanks for getting me this far, budm! What should I do next now that we've come to this point?

[budm]

Re: Vizio E470i-AO - Backlight LED Problem

So one or more of those three strip (each strip has two sub LED strip) may have open circuit at the connectors or open LED, so it is a matter of finding out which one.

[grimacelord]

Re: Vizio E470i-AO - Backlight LED Problem

So one or more of those three strip (each strip has two sub LED strip) may have open circuit at the connectors or open LED, so it is a matter of finding out which one.

Alright. So I'm still checking for continuity and basically go through those strips and sub strips at each connector and LEDs themselves until I find an open circuit?

[budm]

Re: Vizio E470i-AO - Backlight LED Problem

What you can do is to remove one of the three working strip (one strip contains two sub strips) and replaced it with one of three dead strip at a time to find out which one of the 3 strip is bad. One caution, those SMD connectors are very fragile so the solder connection gets broken easily and you have already removed and installed the strips many time so be real gentle with them, I usually re-solder them all for precaution.
This where LED tester come in handy.

[grimacelord]

Re: Vizio E470i-AO - Backlight LED Problem

What you can do is to remove one of the three working strip (one strip contains two sub strips) and replaced it with one of three dead strip at a time to find out which one of the 3 strip is bad. One caution, those SMD connectors are very fragile so the solder connection gets broken easily and you have already removed and installed the strips many time so be real gentle with them, I usually re-solder them all for precaution.
This where LED tester come in handy.

Ok, awesome! Using this method, I have identified two sub-strips that cause the set of 3 to not light. All of the other sub-strips work fine. It's only these two sub-strips. Each are an end that would connect into the green bar first and then another sub-strip would connect into these strips to finish the strip out.

I suppose, and correct me if I am wrong, one or more of these LEDs on these sub-strips has an open circuit and is preventing the rest of the set from working, right? I just have to identify which one. I have replacement LEDs handy. I could just replace ALL of them, since I don't have an LED tester unless you have any other suggestions?

Wow, thanks for the help so far! This thing might actually get fixed today!

[grimacelord]

Re: Vizio E470i-AO - Backlight LED Problem

Pic of bad sub-strips for reference:

[budm]

Re: Vizio E470i-AO - Backlight LED Problem

Ok, awesome! Using this method, I have identified two sub-strips that cause the set of 3 to not light. All of the other sub-strips work fine. It's only these two sub-strips. Each are an end that would connect into the green bar first and then another sub-strip would connect into these strips to finish the strip out.

I suppose, and correct me if I am wrong, one or more of these LEDs on these sub-strips has an open circuit and is preventing the rest of the set from working, right? I just have to identify which one. I have replacement LEDs handy. I could just replace ALL of them, since I don't have an LED tester unless you have any other suggestions?

Wow, thanks for the help so far! This thing might actually get fixed today!

That is correct, you should find out which LED has open circuit, which one may have shorted circuit. Replacing them all may be the best choice.
BTW, look at the bottom side of the strip to see if any of them has brown spot due to over heat.

[SLK001]

Re: Vizio E470i-AO - Backlight LED Problem

These TVs usually fail due to the LEDs opening. Since they are in series, if one goes, they all go for that circuit. Make yourself a simple LED tester by either taping two 1.5V batteries together, or use a power supply, and run the wires to two straight pins. On the good strip, probe the two pins to the LED until it lights up. Once you have gained confidence in your technique, proceed to the bad strip and test every LED. There may be more than one bad, so don't stop at the first bad LED. Once you have found all the bad LEDs, pop off the lens and simply replace them, then TEST your work in circuit and if it works, epoxy the lenses back.

[dskall]

Re: Vizio E470i-AO - Backlight LED Problem

Should you replace individual led's make sure lens is centered over led or you will get bright spots on screen

[budm]

Re: Vizio E470i-AO - Backlight LED Problem

These TVs usually fail due to the LEDs opening. Since they are in series, if one goes, they all go for that circuit. Make yourself a simple LED tester by either taping two 1.5V batteries together, or use a power supply, and run the wires to two straight pins. On the good strip, probe the two pins to the LED until it lights up. Once you have gained confidence in your technique, proceed to the bad strip and test every LED. There may be more than one bad, so don't stop at the first bad LED. Once you have found all the bad LEDs, pop off the lens and simply replace them, then TEST your work in circuit and if it works, epoxy the lenses back.

I would suggesting using current limiter power supply or if you batteries is to limit the current because if the applied Voltage is backward, the protection diode (which is connected in anti-parallel with the LED, not all LED has protection diode) will be fully conduct due to 3 Volt being applied to 0.6V diode junction so you can short out the protection diode. Always limit the current for protection in case of wrong connection.

[grimacelord]

Re: Vizio E470i-AO - Backlight LED Problem

So, I wanted to post back an update. I was able to desolder the LEDs from the LED strips I mistakenly bought and solder them onto the original LEDs strips for just ONE of the strips. The others didn't seem to want to work. In the interest of time, I purchased the remaining strips I needed and just received them. I connected them all back together, and now all of the strips are fully illuminated!

So now I will begin reassembly and I will show the final working product (hopefully!)

Thanks for all the help and hopefully reassembly is without problems. Attached a picture of fully illuminated LED strips for reference.

[grimacelord]

Re: Vizio E470i-AO - Backlight LED Problem

Awesome! Works! Thanks a ton, budm! I've learned quite a bit more about how these TV's operate from reading your posts and throughout this exercise! I'm sure I'll ask for help again in the future.

Attached pic of working TV for reference.

[budm]

Re: Vizio E470i-AO - Backlight LED Problem

Thanks for the follow-up on the repair.