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    Vizio E701A3 No picture

    Hello guys. I'm new here but I have done a fair amount of research on this TV. Long story short I picked this 70" TV as non working unit for $20 today. Yes I know they were recalled. However according to the serial number this one was not one of the affected units. Anyway this TV is 4 years old. The person I got it from told me he was watching the TV and it just went out and would not power on. I knew when I got it that they were recalled and known to have the infamous black screen of death and that the lcd panel itself goes bad. I figured for $20 its worth a shot in the dark. I'm a automotive technician by trade and have done my fair share of electrical nightmares on luxury cars. So nothing surprises me anymore. Also on that note yes I know there are numerous threads on this particular TV. I have been through most of them but couldn't find the answers I am looking for. So onto the details.

    The previous owner stated tv just stopped working would not come back on. He wasn't able to tell me wether it still had sounds or not. He did say before it went out it made a very bight flash and went out.

    So fast forward to me tear down and diagnosis. When I got it home I did a hard reset and discharged the capacitors as well. To no avail,when powered one the led would flash a few times and go back out. Then I could turn it on the whole screen would flicker and go out and make this static type noise like something was shorted. Also by screen I mean the back light would flicker once and go out. So I thought ok maybe just the back light circuit is the issue or the power supply board as the circuit is on that board.

    So I took the back panel off removed the power supply board and inspected it closely at first I didn't see anything but after flexing the board here and there I found 2 cold solder joints on one of the yellow capacitors on the board. So I resoldered the 2 clearly cracked joints and viola the back light was fixed and now the TV stays one just no picture. So with the back light issue sorted I thought maybe I have a power supply issue or standby power issue from power supply board to the main board.

    But I checked standby power and it shows 3.3volts so I know thats good. So I decided to check the remaining pins and it all looks good except for the main board. So I am getting 12v in pin 1 on one of the ribbon cables going to the TCON board but nothing on the second ribbon cable on pin 1. This panel is split into 2 halves. It looks like the main board isn't sending 12v out to one side of the panel. So when checking the TCON board and checking the contactor I get 15.5v on the drain,gate gets 0volts as does the source. I had luck disconnecting the one ribbon cable from TCON board and only half the screen was working but had some lines through it. Now I cant get it to do anything. My question is this, could my issue be the main board as its not sending out 12v for the second ribbon cable. I mean this makes sense. being that before I could disconnect one ribbon and have half the panel working but now I still only get 12v on the one ribbon cable but the panel is dead nothing works even when disconnecting the other ribbon to have half the panel work. I am open to suggestions. Wondering if theres any more diag that can be done on the main board before replacing it.

    #2
    Re: Vizio E701A3 No picture

    Probably panel fault, there's a little light reading there, outa cover it: https://www.badcaps.net/forum/showthread.php?t=49281

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      #3
      Re: Vizio E701A3 No picture

      I already read that. Thank you for the suggestion but I’m more concerned why isn’t the main board supplying 12v to the other half the panel. Also when I had disconnected the left side ribbon cable I had a no signal image show up o. The right hand side of the screen but it’s wasn’t very clear. I think I made the mistake of doing it while the tv was turned on and possibly shorted the TCON board. Either way I ordered some parts. Now it’s just a waiting game.
      Last edited by Euroxs4; 08-03-2020, 06:51 AM.

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        #4
        Re: Vizio E701A3 No picture

        probably a dumb question, but how do you know that the cables (which cables are you referring to?) are the same in terms of pins / signals?

        Comment


          #5
          Re: Vizio E701A3 No picture

          Originally posted by budwich View Post
          probably a dumb question, but how do you know that the cables (which cables are you referring to?) are the same in terms of pins / signals?
          I have watched a few videos in regards to this tv for troubleshooting followed the video mostly checked the pins mentioned for voltage. I couldn't find a service manual for this tv anywhere, But I know the tv boots and has sound as I had my firestick connected to it and it had sound when the firestick boots. If you want I can attach some pictures or a link to the video in question.

          Are you asking about the 2 ribbons where one is not getting 12v from the main board??They are not identical, the pin that gets a 12v supply for the left side of the panel is the bottom pin IIRC pin 41 where as the right side of the panel get 12v at pin 1 both at the main board.
          Last edited by Euroxs4; 08-03-2020, 07:04 AM.

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            #6
            Re: Vizio E701A3 No picture

            I am just going by what you posted about 12v which indicated pin 1 on one cable and pin 1 on the other.... that's all the question was about.

            It is likely that once you did a few more "things" that potentially a component (eg. fet) died which it now appears that you are waiting on.

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              #7
              Re: Vizio E701A3 No picture

              Yes sorry it was my mistake. So ribbon for the right side of the panel gets power on pin 1 should have 12 volts and i have 12 volts there at the main board and at TCON board. However ribbon for left side of the panel should have 12v on pin 41 at the main board. However I do not have 12v at pin 41. This is why im questioning wether I have a bad main board as well. I think its safe to say TCON is toast. I think the next course of action is gonna be replacing main board and TCON and leaving both ribbons to panel disconnected. Then power up the tv and check my readings at TCON and mosfets on the board. Then ill connect right side panel as I had a picture on that side initially to see if I have any picture at all. Then ill gamble and hook up the left side and say a hail mary it doesnt burn up the mosfet on the TCON board. Sounds about right?

              Comment


                #8
                Re: Vizio E701A3 No picture

                Has anyone been in the service menu and altered the Panel type?
                Willing to help but I'm no expert.

                Comment


                  #9
                  Re: Vizio E701A3 No picture

                  Originally posted by dick_barton View Post
                  Has anyone been in the service menu and altered the Panel type?
                  I doubt it. I picked it up from the previous owner. He didn't mention anything other than its went blank while he was watching it. I haven't been able to get into any menu as it displays no image. When I had the left side ribbon at TCON disconnected I had a no signal image on the right side of the screen. But it had some yellow text and wasn't defined and very clear. After I reconnected the left side ribbon at TCON no image at all. Even now. I dont think the panel is shorted as owner didnt mention horizontal or vertical lines in the screen before failure. I think if that was the case was could say a panel is shorted. I also looked at serial number but it didnt match the range of the recalled ones. I think main board issue causing TCON to fail I hope. Whats the best way to test new TCON before hooking it up. Can I do just resistor values across all the transistors?

                  Comment


                    #10
                    Re: Vizio E701A3 No picture

                    Originally posted by Euroxs4 View Post
                    Yes sorry it was my mistake. So ribbon for the right side of the panel gets power on pin 1 should have 12 volts and i have 12 volts there at the main board and at TCON board. However ribbon for left side of the panel should have 12v on pin 41 at the main board. However I do not have 12v at pin 41. This is why im questioning wether I have a bad main board as well. I think its safe to say TCON is toast. I think the next course of action is gonna be replacing main board and TCON and leaving both ribbons to panel disconnected. Then power up the tv and check my readings at TCON and mosfets on the board. Then ill connect right side panel as I had a picture on that side initially to see if I have any picture at all. Then ill gamble and hook up the left side and say a hail mary it doesnt burn up the mosfet on the TCON board. Sounds about right?
                    you don't have to gamble. I do believe there is a simple resistance measurement associated with the output of the fet (to ground) to see if there is a short in the "subtending" tracks for each side. You might find something on here for the test as I think there have been posts about it. Having said that, it would seem "natural" that if you have the card disconnected from the main (ie. no input powering) and then hook up one tcon to panel cable at a time and do the resistance measurement mentioned previously, you should see the difference between the sides.... one having very low resistance and the other, somewhat normal.

                    Comment


                      #11
                      Re: Vizio E701A3 No picture

                      Originally posted by budwich View Post
                      you don't have to gamble. I do believe there is a simple resistance measurement associated with the output of the fet (to ground) to see if there is a short in the "subtending" tracks for each side. You might find something on here for the test as I think there have been posts about it. Having said that, it would seem "natural" that if you have the card disconnected from the main (ie. no input powering) and then hook up one tcon to panel cable at a time and do the resistance measurement mentioned previously, you should see the difference between the sides.... one having very low resistance and the other, somewhat normal.
                      So yes I hear what your saying. I have done that test, resistance reading using the cathode side of the diode With the left side ribbon disconnected from TCON I was seeing 9.4kohms which from the research ive done is acceptable anything between 9-10kohms. With the left and right side connected I was seeing 1Kohm. This means the left side panel is shorted. However the fact that I dont have 12v for that panel bother me as I think that would affect that circuit. I guess in short the left side panel is most likely shorted and the only option is to perform operation and remove the driver tabs as some other have done on here.

                      I used this video for my check:

                      https://www.youtube.com/watch?v=cyCKoMi_5IA
                      Last edited by Euroxs4; 08-03-2020, 12:18 PM.

                      Comment


                        #12
                        Re: Vizio E701A3 No picture

                        there is also a potential for the same test to somewhat check if the issue is in the bottom edge boards as opposed to the side. There is "u" type ribbon cables interconnecting the bottom edge boards together on each "half side". You can disconnect the ribbon and do the same resistance check again and compare the results. This will tell if the problem lies beyond the "middle quarter" of the bottom edge board. Further, I can't remember if this set has small ribbon cables at each corner at the bottom which interconnect the bottom to the side. IF it does, the same check can be done again and go from the results. The reason for doing this many "things" is to make sure you have exhausted all check and determine that the problem is indeed with the side as removing tabs is a "final activity" and can't be replaced / returned. Some times, there are SMD components on the bottom edge boards that can be a problem plus also sometimes the interconnecting cabling is an issue and just needs to be cleaned / reseated. It would be disappointing if the side tabs were removed when the problem was elsewhere.

                        Comment


                          #13
                          Re: Vizio E701A3 No picture

                          Originally posted by budwich View Post
                          there is also a potential for the same test to somewhat check if the issue is in the bottom edge boards as opposed to the side. There is "u" type ribbon cables interconnecting the bottom edge boards together on each "half side". You can disconnect the ribbon and do the same resistance check again and compare the results. This will tell if the problem lies beyond the "middle quarter" of the bottom edge board. Further, I can't remember if this set has small ribbon cables at each corner at the bottom which interconnect the bottom to the side. IF it does, the same check can be done again and go from the results. The reason for doing this many "things" is to make sure you have exhausted all check and determine that the problem is indeed with the side as removing tabs is a "final activity" and can't be replaced / returned. Some times, there are SMD components on the bottom edge boards that can be a problem plus also sometimes the interconnecting cabling is an issue and just needs to be cleaned / reseated. It would be disappointing if the side tabs were removed when the problem was elsewhere.
                          Yes this tv does have the u type ribbon on the bottom boards and small ribbon cables corners. So I disconnected the small ribbon cable on the left bottom corner of the panel and I am getting 9.4kohms this tells me the panel is good but the tabs running on the left side a FUBAR.Correct?
                          Last edited by Euroxs4; 08-03-2020, 01:49 PM.

                          Comment


                            #14
                            Re: Vizio E701A3 No picture

                            that would be my "read". Having said that, when you fix or replace your tcon, you can run with the corner cable disconnected without causing any problems to the tcon or set. Depending on what the resulting picture is, it will finally confirm the issue is somewhere along the side.

                            Comment


                              #15
                              Re: Vizio E701A3 No picture

                              Originally posted by budwich View Post
                              that would be my "read". Having said that, when you fix or replace your tcon, you can run with the corner cable disconnected without causing any problems to the tcon or set. Depending on what the resulting picture is, it will finally confirm the issue is somewhere along the side.
                              I am in agreement this is the best course of action. Now just a waiting game for the replacement TCON. However I also ordered a main board just in case. As I still dont know why the main wasnt sending out 12v for the left side of the panel. Maybe because its shorted?? I am not too familiar with TV circuits but new automotive circuits are turned of via control module if a short is detected curious if this is possible in this case. My logic says yes it the smart thing to do and the right approach but then again this tv is known for defective panels and blow mosfets on TCON board instead of a fuse so clearly their logic is flawwed. It would be nice to get this thing up and running. Its going to be a TV in my garage would be nice to get it up ad running. I will post once I have the parts. Thanks for the advice and input.

                              On that note can the corner be left disconnected or do the tabs need to be completely removed?
                              Last edited by Euroxs4; 08-03-2020, 02:07 PM.

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                                #16
                                Re: Vizio E701A3 No picture

                                IF indeed that the side is bad, they have to be removed. IF you do the "live test" that I suggested with the corner cable, you will see why... :-)

                                Comment


                                  #17
                                  Re: Vizio E701A3 No picture

                                  Originally posted by budwich View Post
                                  IF indeed that the side is bad, they have to be removed. IF you do the "live test" that I suggested with the corner cable, you will see why... :-)
                                  What is the best way to remove them?? Can the ribbons be cut away instead of being pulled off or is the key to remove the ribbon thats stuck to the board?? If so what is the best method heat?

                                  I will make sure to take some pictures and video once I get the replacement TCON board.

                                  Comment


                                    #18
                                    Re: Vizio E701A3 No picture

                                    they are just like removing pieces of tape... gently pull them up and away from the panel.

                                    Comment


                                      #19
                                      Re: Vizio E701A3 No picture

                                      Well I ordered a repair kit for the TCON board. It was 3 mosfets. I soldered them in. I went to do a test run and one of the mosfets proceeded to light itself on fire. I will attach pictures. The question is why? I think possibly solder bridge but I was careful so who knows. Really tiny components its possible. I still had the corner ribbon cable disconnected. Also note I installed a repalcement main board. Its still not putting out 12V on one channel. So thats weird. Mosfet circled is the one that decided it was time to Now I have to wait for the replacement TCON I ordered. Im guessing I should send the main board back as it didnt change anything.
                                      Attached Files
                                      Last edited by Euroxs4; 08-07-2020, 06:19 PM.

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                                        #20
                                        Re: Vizio E701A3 No picture

                                        Ok so I this configuration with new tcon board installed I have 9.4k ohms. That’s good with ribbons connected to lcd panel but nothing connected from main board and corner ribbon disconnected. However with the left corner ribbon connected it reads 1300ohms so It looks like the left side is the issue correct??

                                        Also I did a dry run L lower corner cable disconnected. Both ribbons to tcon connected and both ribbons to lcd panel connected The menu works however right side of the screen does not display anything. Any ideas??
                                        Attached Files
                                        Last edited by Euroxs4; 08-11-2020, 05:50 PM.

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