Vizio E7-E3 Black Screen

[BobbyG58]

Re: Vizio E7-E3 Black Screen

1) So I look at the SJ video, each LED string has 9 LED's, two LED strings are connected together so both strings use 1 common red wire and two black return wires, one for each string, that is why you have total 6 red wires and 12 Black wires.
So if they are 3V LED, then total Vf (Forward Voltage for each string will be about 3V x 9 LED's = 27V, if they are 6V LED's then total Vf for each string will be 6 x 9 = 54V.
You indicated that you do have 57V feeding the Anode of each LED string so I expect to see Voltage at the Black return wire of the LED string, but you indicated all 0V which does not make sense that all 12 LED strings went open circuit.

2) About the two main filter caps that shows about 300VDC instead of typical 380 ~ 400 VDC, those two caps are connected in parallel, so that will not be the cause of the half screen problem.

3) Your LCD panel looks to be made by Sharp, and these Sharp LCD used in many 70" TV's and typical failure is due to side tab driver, which based on your prescription about half screen is dark seems to point to the problem on the panel, the T-CON on this TV also controls the backlights so you may want to try disconnecting those 4 flat ribbon cables between T-CON and the LCD panel to see what happen. It may be that the T-CON is locking down the backlights circuit. BTW, when you say half screen is dark, is it like completely black? Or something like this: https://www.reddit.com/r/VizioTV/com...n_vizio_e70e3/

4) The main board IC U400 is the LED driver, what is the P/N of that IC?

Hi Bud, on your points.

1) When I looked at the E70-E3 LED replacement video on youtube, what I saw, correct me if I am wrong, was 6 rows with two strips per row.
1 Full row/ 2 strips = 18 LEDs with 9 per strip 9x2. If as you say VF = 3.1v x 18 =55.8v per row.
Maybe I am not thinking correctly. As you mentioned 1 red per row and one black per strip.
As for the black wires, I am not familiar with how an LED circuit works but if I understand correctly, there SHOULD be in this case of 57v per red, 28.5v(57v/2) on each black wire?

2) With both of those being low, would that indicate a faulty PSB in addition and irregardless to whatever else is going on with the LEDs? Replacement/ repair PSB?

3) I will have to ask my brother on this. He asked me about the "half black" some time ago but never addressed it at that time until it went full black as it is now. Answer later today after I ask him and I will try disconnecting the T-Con ribbons from the panel.

4) I will get the part number for IC U400 later today.

Thanks again. You are teaching an old dog new tricks.

[BobbyG58]

Re: Vizio E7-E3 Black Screen

Maybe check those little capacitors on tcon for shorts, diode mode, probe on each side, tv unplugged.

Do you mean the 3 silver "can"capacitors? I can check those later today if those are the ones you are thinking.

[budm]

Re: Vizio E7-E3 Black Screen

Hi Bud, on your points.

1) When I looked at the E70-E3 LED replacement video on youtube, what I saw, correct me if I am wrong, was 6 rows with two strips per row.
1 Full row/ 2 strips = 18 LEDs with 9 per strip 9x2. If as you say VF = 3.1v x 18 =55.8v per row.
Maybe I am not thinking correctly. As you mentioned 1 red per row and one black per strip.
As for the black wires, I am not familiar with how an LED circuit works but if I understand correctly, there SHOULD be in this case of 57v per red, 28.5v(57v/2) on each black wire?

2) With both of those being low, would that indicate a faulty PSB in addition and irregardless to whatever else is going on with the LEDs? Replacement/ repair PSB?

3) I will have to ask my brother on this. He asked me about the "half black" some time ago but never addressed it at that time until it went full black as it is now. Answer later today after I ask him and I will try disconnecting the T-Con ribbons from the panel.

4) I will get the part number for IC U400 later today.

Thanks again. You are teaching an old dog new tricks.

1) As I explained how the LED strips are connected, you have 12 LED strings = 12 Return black wires, 1 wire is shared by two LED strings so that is why it has 6 red wires. Each LED string has 9 LED's and 12 LED drivers, each driver drives 9 LED's.
May be you need to invest in LED tester so you can test the whole LED string without opening the panel.

[BobbyG58]

Re: Vizio E7-E3 Black Screen

I understand, However you had mentioned voltage on the black wires. In this case of 57v on the Red, should each black show half of the 57v?
Right now of course I get 0v on those. But when all is working should they read half of the 57v?

If I purchased an LED tester, could I unplug the connector from the main board and probe one red wire and just probe each black wire until I hit the correct corresponding black wire to light the strip?

[budm]

Re: Vizio E7-E3 Black Screen

57V is fed to the Red wire which is Anode pin of the LED string, the Black wire is the Cathode return which the current returns to GND via the PWM controlled MOSFET and the current sensing resistor.
When it is working , the Voltage on the black wire will depend on what the total Vf of the LED string is, the Voltage on the black wire is the Voltage drops of the MOSFET + Vdrops of the current sensing resistor, typical is about 10 ~20V range.
"If I purchased an LED tester, could I unplug the connector from the main board and probe one red wire and just probe each black wire until I hit the correct corresponding black wire to light the strip?" That is correct.

[BobbyG58]

Re: Vizio E7-E3 Black Screen

Ok, I unplugged the T-con from the panel, no change. I reconnected the panel and disconnected the VSNS cable and no change.
In regard to probing the black wires, I should find 2 corresponding black wires to 1 red wire?

The U400 is an AS3820

I also went back and looked at the youtube video. It appears that the output from the main board plugs directly into each strip. i.e. no board in between the MB and the LED strips.

[budm]

Re: Vizio E7-E3 Black Screen

"It appears that the output from the main board plugs directly into each strip. i.e. no board in between the MB and the LED strips." that is correct, you see only one red wire because it is shared between the two LED strips (1 row of LED strip).
AS3820 LED driver, see how the LED's string are driven as I already explained.

[nomoresonys]

Re: Vizio E7-E3 Black Screen

Do you mean the 3 silver "can"capacitors? I can check those later today if those are the ones you are thinking.

No, the little brown ones on the tcon.

[BobbyG58]

Re: Vizio E7-E3 Black Screen

"It appears that the output from the main board plugs directly into each strip. i.e. no board in between the MB and the LED strips." that is correct, you see only one red wire because it is shared between the two LED strips (1 row of LED strip).
AS3820 LED driver, see how the LED's string are driven as I already explained.

I looked at the pdf, Although I can recognize many components in a schematic, I won't even pretend what it is telling me about what it is doing and about no return voltage on the black return wires. Could a bad U400 cause this issue?

[BobbyG58]

Re: Vizio E7-E3 Black Screen

No, the little brown ones on the tcon.

I counted around 30. Any idea where on the board I would be looking?

[nomoresonys]

Re: Vizio E7-E3 Black Screen

Start with the ones on the side that went black first.

[nomoresonys]

Re: Vizio E7-E3 Black Screen

Starting at 10 bucks, I would try a tcon, think these are it by part number but as always, triple check to make sure its a match. https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

[BobbyG58]

Re: Vizio E7-E3 Black Screen

Starting at 10 bucks, I would try a tcon, think these are it by part number but as always, triple check to make sure its a match. https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

Wow, I searched right before you sent this and only found $20-$60, thanks.

Back to the PSB low voltage caps, should I think about a new PSB also?

[nomoresonys]

Re: Vizio E7-E3 Black Screen

Your call but if they're pretty reasonable in price, might not hurt to have a spare psb, might be a good way to eliminate it as a suspect if you get a good one.

[nomoresonys]

Re: Vizio E7-E3 Black Screen

Think these are it. https://www.ebay.com/sch/i.html?_fro...=RUNTK0228FVZZ

[nomoresonys]

Re: Vizio E7-E3 Black Screen

.

[BobbyG58]

Re: Vizio E7-E3 Black Screen

Your call but if they're pretty reasonable in price, might not hurt to have a spare psb, might be a good way to eliminate it as a suspect if you get a good one.

I was just watching a YT video on PSB. In that video, the two capacitors that I checked on my board you mentioned a PFC and in the video the guy had a similar situation where Budm told him that his board had no PFC and that his low voltage of 360v would be normal.

I am wondering how I tell if the board has a PFC and if my board might be similar to the one in the YT video?

My thinking right now is if my 297v is too low for this board, then I should replace the PSB first and eliminate any power supply issues and then continue with my diagnosis.

If the voltage in normal for this board with no PFC, then I can definitely rule out any power supply issue and then question the Main logic board at the AS3820 U400 IC. Since I do not understand what that chip does, I am kind of stuck on why I do not have any return voltage from the strips and if the IC could somehow cause a no return voltage or should there always be return voltage if the strip(s) is good?

At this time, I do not have an LED tester so I am stuck with eliminating any board issues.

[budm]

Re: Vizio E7-E3 Black Screen

Your power supply board has PFC Voltage booster.
T101 is the PFC inductor, Q101 is PFC MOSFET.
Shopjimmy sells the board set for reasonable price: https://www.shopjimmy.com/catalogsea...q=VIZIO+e70-e3

[BobbyG58]

Re: Vizio E7-E3 Black Screen

Your power supply board has PFC Voltage booster.
T101 is the PFC inductor, Q101 is PFC MOSFET.
Shopjimmy sells the board set for reasonable price: https://www.shopjimmy.com/catalogsea...q=VIZIO+e70-e3

Thanks Budm, I use SJ from time to time. I see they have a full board set for a good price. I may just go that route.

Can you answer one more question please?

I am still confused about the voltage on the black leads coming back from the strips.

Not fully understanding why there is voltage going in but not coming back.

In my simple mind, I am thinking about water flow with a single hose feeding both strips and a hose on each strip coming back with equal water flow from each of the strips or half of the water going in. What happened to my two water supplies coming back?

Sorry to be such a newbie but I am trying to learn.

[budm]

Re: Vizio E7-E3 Black Screen

"Not fully understanding why there is voltage going in but not coming back." That is still puzzle to me too.