Vizio M470NV LED LCD Help Needed!

[70JUDGE]

I'm looking at a Vizio LED TV that turns on,shows the Vizio logo,then the screen goes dark with sound,and a picture if you shine a light on the screen.I know on a traditional LCD TV there is either an inverter,or a set of them that light up the screen,and can go bad,but what about an LED LCD TV?What lights up the LED bulbs?Does the whole screen need to be replaced?Any help is greatly appreciated.Thank You very much!

Tyler

[tom66]

Re: Vizio M470NV LED LCD Help Needed!

Well, perhaps the same thing happens with LED TVs, if an LED has failed (for any reason) then maybe the entire array will not function properly.

Sourcing LEDs may be tricky.

Could also be a power supply or LED power supply problem.

[70JUDGE]

Re: Vizio M470NV LED LCD Help Needed!

I take it the TV doesn't need any type of inverter like in a regular LCD TV?What voltage is supplied to the LEDs?Is there still a safety concern so if one light goes out,the whole display goes out like it does with the CCFL bulbs even though there isn't the same high voltage needed?Does anyone know where I can find a Service Manual?Thank You very much!
Tyler

[tom66]

Re: Vizio M470NV LED LCD Help Needed!

I take it the TV doesn't need any type of inverter like in a regular LCD TV?What voltage is supplied to the LEDs?Is there still a safety concern so if one light goes out,the whole display goes out like it does with the CCFL bulbs even though there isn't the same high voltage needed?Does anyone know where I can find a Service Manual?Thank You very much!
Tyler

LEDs are current controlled, similar to CCFLs, although they do not use a low voltage. By applying a fixed voltage to the array a fixed current flows and this is used to regulate the brightness. They may be series wired, in which case like xmas lights, if one fails the entire array will fail. It's possible there are multiple series strings, or they are in parallel.

If it's a full LED display then each small group is controlled differently, the above does not apply.

[70JUDGE]

Re: Vizio M470NV LED LCD Help Needed!

It is an edge lit TV.
Are the bulbs low voltage?Can they be tested with a separate power supply,or are they like CCFL,they can test good by themselves,but draw enough current in the TV to shut it down?
Does the whole panel have to be taken apart like a CCFL to get to the LEDs?How expensive are the LED bulbs?How often do the bulbs go bad?More or less then the CCFL?
By the TV showing the Vizio logo before going dark,does this mean the LCD screen,T-Con,and Mainboard are alright?
Is there a Service Manual somewhere,or is it too new of a TV?

Thank You very much!
Tyler

[tom66]

Re: Vizio M470NV LED LCD Help Needed!

It is an edge lit TV.
Are the bulbs low voltage?Can they be tested with a separate power supply,or are they like CCFL,they can test good by themselves,but draw enough current in the TV to shut it down?
Does the whole panel have to be taken apart like a CCFL to get to the LEDs?How expensive are the LED bulbs?How often do the bulbs go bad?More or less then the CCFL?
By the TV showing the Vizio logo before going dark,does this mean the LCD screen,T-Con,and Mainboard are alright?
Is there a Service Manual somewhere,or is it too new of a TV?

Thank You very much!
Tyler

The LEDs are low voltage, typically 3.5V each. But they are usually in a series string. Maybe 10-20 LEDs per string, so the array could have 70V across it and be capable of providing several hundred milliamps. Could give a nasty shock.

LEDs usually cannot be replaced individually as they are on flexible membranes. But they rarely go bad, unless they have insufficient cooling, in which case they can last only a year or so.

The t-con etc. could be okay but they could be shutting down due to faulty LED driver or LEDs.

[PlainBill]

Re: Vizio M470NV LED LCD Help Needed!

This is pure speculation on my part; I haven't been able to find any useful information on the design of LED backlights. To me the sensible way to design these would be a number of LEDs in a series string, with as many strings as necessary in parallel. Rather than using only a resistor to limit current, using a transistor and a current sense resistor for each string makes more sense, especially since the control part could be incorporated into a single IC controlling multiple strings. And of course, 'open string' sensing is trivial in a case like this.

PlainBill

[70JUDGE]

Re: Vizio M470NV LED LCD Help Needed!

Is there a Service Manual somewhere,or is it too new of a TV?

Thank You very much!
Tyler

[PlainBill]

Re: Vizio M470NV LED LCD Help Needed!

Is there a Service Manual somewhere,or is it too new of a TV?

Thank You very much!
Tyler

The best source of service manuals I've found is elektrotanya. Vizio service manuals are very hard to find. Further complicating the situation is the LCD panel and backlights are usually treated as an unrepairable unit, no service information is included.

PlainBill

[GbreadMan]

Re: Vizio M470NV LED LCD Help Needed!

There's certainly a service manual somewhere, but it's a pretty new model. You'd need to find a current warranty repair tech.

Dan

[70JUDGE]

Re: Vizio M470NV LED LCD Help Needed!

Does anyone know where I might find a set of replacement LEDs?The numbers on them are 3660L-0348A Housing(L),and 3660L-0349A Housing(R).They also say LG on the LED strips themselves.I need two of each.

I tried a different power supply,and it did the same thing.Next I tried a set of LEDs from a broken panel that someone had online.Before taking the panel apart,I plugged the new LEDs into the new power supply with LEDs outside the TV,and they lit up,and stayed on.

When I took the panel apart,and replaced the LEDs,I put the old power supply in the TV instead of the new power supply I used to test the new LEDs with thinking there was nothing wrong with old one because it didn't fix the problem,and it did the same thing again.

I tried using the new power supply after,and it didn't make any difference.The only thing I can think of is by using the old power supply first instead of the new one,I burned out the new LEDs,and by the time I put the new power supply in,the damage was already done.

I even tried to set the original set of LEDs up outside the TV like I did with the new ones,and all of them light up,but when they go out,one strip is completly out,and the other three strips have a few lit up here,and there,and they are real dim.It also does this for a split second as soon as I press the power button before they come on full brightness for a few seconds,and then go off.This happens with bothe power supplies.

The funny thing is the backlight on wire still has 3VDC,on it as well as 115VDC to each of the LED strips.There are also three other wires to each LED strip that have anywhere between a little over 10VDC,to a little over 12VDC.This is with both power supplies,so I don't know what in the original power supply would be burning out the LEDs,or what is turning the LEDs off.If the main board is,shouldn't the voltage on the backlight on wire go away?If the LEDs,or one of them are bad,why are they all lighting up?Also,what is the 10 to 12 volts for on the other three wires for each of the LED strips?Shouldn't the 115V be enough?

There are two LEDs strips on the top,and two on the bottom.Each strip has 66 LEDs,and has a trace that runs the length of the strip.There are three other traces that each go a third of the way down the strip.On the power supply the connections are marked VLED 1-1 1-2 1-3,VLED 2-1 2-2 2-3 ETC. for each of the four LED strips.With the LEDs plugged in,I get 115VDC on each of the VLED,and anywhere between a little over 10VDC,to a little over 12VDC on the numbered wires.I would unplug the connectors,and test the power supply,but I don't want to take a chance on the power jumping to another pin like it did on me with the Proscan 40LD45Q.Maybe that was because it was a higher voltage.

The only thing I can think of to do is to get another set of LEDs,and try them outside the TV with the new power supply like I did before,and if they work,put them in with the new power supply.

Any help is greatly appreciated.Thank You very much!

Tyler

[angrydingo]

Re: Vizio M470NV LED LCD Help Needed!

was any progress ever made on this issue? I'm having the same issue with my m470nv :-(

[goontron]

Re: Vizio M470NV LED LCD Help Needed!

check any mosfet's in the circlet

[70JUDGE]

Re: Vizio M470NV LED LCD Help Needed!

It turned out to be the LED backlights,as well as the power supply.I had tried another power supply at first,but it didn't make any difference.Then I tried a set of backlights I had bought from a TV with a broken panel,and the TV would stay lit.This was using the new power supply,with the new LEDs outside the TV.In the process of putting the TV back together,I installed the old power supply thinking there was nothing wrong with it,and the TV was back to turning on,and going dark after a few seconds.Even with the new power supply.You could still see a picture if you shined a light on the screen.

After hunting all over for just the backlights,I ended up buying a complete TV with a broken screen,and this time,I used the backlights,as well as the power supply,and the TV has been working ever since.The funny thing is the backlights have part numbers on them,but I couldn't find anyone that had them.I hope this helps. Please let me know.Thank You very much!

Tyler

[budm]

Re: Vizio M470NV LED LCD Help Needed!

And yet they claimed 50,000 Hours on the LED! Seems like bad design.

[70JUDGE]

Re: Vizio M470NV LED LCD Help Needed!

What they should do is put a 50,000 hour warranty on the power supply.I doubt that will happen.It's like their bright pixel policy.Why not a dead pixel policy like everyone else?
I see online there are alot of other people having the same problem.I almost want to say it is in the connector at the end of the LED strips.I managed to pull one off while changing mine out.Good thing it was on the old strip.Thank You very much!
Tyler

[angrydingo]

Re: Vizio M470NV LED LCD Help Needed!

how do you get at the leds to change them? do i need to remove all the boards and take that metal chassis off and get the actual screen out?


also, would the replacement LEDs need to be the exact same model #?

[70JUDGE]

Re: Vizio M470NV LED LCD Help Needed!

I took all the boards off from mine so there would be less of a chance of something breaking when the TV was flipped over to remove the screws,and metal trim around the screen.If you can find a way to support the screen off where you are working on it,you can leave the boards on.The front trim has to come off to get to the screws,and metal trim holding the panel in place.I installed the stand screws on the ends of the panel trim to hold the glass in place when the TV was flipped back over.Once you remove the front screws,there isn't anything but wires holding the glass in place.Wires that are bonded to the glass panel to be exact.You also have to undo the clips around the outside of the screen,and carefully undo the clips on the T-con side of the panel before the back will come off.I used a plastic puddy knife for this.I suppose an old credit card would work as well.

I would try to stay with the same exact model.I noticed all the boards,as well as the LEDs were labeled LG.I tried to find out which model LG LED TVs used the same LED strips from LG,but they didn't know,and I couldn't find anyone else that knew either.
I hope this helps.Please let me know.Thank You very much!

Tyler

[angrydingo]

Re: Vizio M470NV LED LCD Help Needed!

alright, so I tried a new power supply tonight, to be exact, i took a fuse off one that i bought on ebay and soldered it onto the original psu that had blown a fuse. Now the backlight comes on for 2 seconds and shows the vizio logo and then flicks off. With the other psu, the vizio logo never came up.

I can still see the image if i hold a flashlight to the screen.

I know in your post you said you had the same thing and it ended up being the LEDs. I just found it curious that with this PSU the vizio logo now comes up. Any chance its anything else? i really doubt ill be able to find this exact tv with working LEDs to replace them

Anyone?

[angrydingo]

Re: Vizio M470NV LED LCD Help Needed!

the most incredible thing just happened.....

so i left the tv on with no backlight for awhile after it went to the v-logo and backlight went dim. vizio logo stayed illuminated white as it usually does. Turned off TV with remote and turned back on.

POW, vizio logo, BACKLIGHT ON. everything seems to be working

just turned it off and back on. BACKLIGHT ON AGAIN. lol

aaaaaaaand now im scared to touch anything. lol