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CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

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    #1

    CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

    Hi All. I need some help confirming if I have a bad panel.

    Got this one with no picture but the backlights are working. Previous owner tried replacing both main board and t-con with no joy - he gave me the extra boards too. I was guessing it would turn out to be bad panel and I'd strip it for what very few parts are worth keeping. Or with a bit of luck was hoping for a shorted cap on a driver board for a cheap fix.

    Usually when I get one like this after checking voltages on t-con I do the test of disconnecting one side of the panel at a time at the ribbons to the t-con and more often than not get one half working with picture and the other side not working confirming a panel issue. Also I've normally found the bad panel/drivers pull down voltages on the t-con when the faulty side is connected.

    This time though when disconnecting one half of the panel, the disconnected half turns full white and the connected side is dark with no picture, and it does the same thing on either side. Voltages appear to be fine on t-con in all configurations.

    What's going on here with this test and how can I confirm if the panel is bad or not?
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    #2
    Re: CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

    verify the lvds signal on the main board to the tcon with an oscilloscope, while turning the menu on and off all the time when you are probing around. Only because the boards were replaced, doesn't mean they are good to begin with. So verify the main is working, then check the tcon. Also don't source boards from ebay etc. I wouldn't trust most of those sellers.

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      #3
      Re: CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

      Sadly I don't have an oscilloscope. I tried loosening and wiggling the lvds connector at the t-con a bit to see if I could provoke a response from the panel and a few times very briefly saw a couple of one pixel lines appear right across the screen.

      I'm currently connected up to the main board via serial cable to see what's going on but part way through boot up it says UART disabled and then nothing. Annoyingly it must be disabled in the service menu. Both main boards I have behave exactly the same way giving the same messages on the terminal. They both will respond to remote control signal to shutdown although I have no indication whether they are responding to anything else.

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        #4
        Re: CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

        Maybe you could borrow a oscilloscope from a friend? Other than that, I guess you are SOL, because you just don't know what board to replace. If a working TCon could be had for cheap from a reputable seller or store, I would try that. Other than that you really have to know that the main board is actually put something out on the LVDS, or keep gambling buying more boards, or scrapping it.

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          #5
          Re: CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

          Thanks, I will see if I can get hold of a scope. Though the boards are so cheap on this I may take a chance on another t-con and main in the meantime.

          I guess I'd be surprised to find out the main boards/t-cons are bad because the voltages on the t-con are correct and usually when these mains go bad they bootloop or don't respond to the remote. I haven't heard of one that doesn't output video so getting two that do that seems slim. Anyway it's all theoretical until I can check with a scope. Just curious if there is a failure mode of a panel that would not affect t-con voltages and would not change with disconnecting left/right panel ribbons.

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            #6
            Re: CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

            So got hold of a scope finally. I do see activity on LVDS connector when hitting the menu button so looks like the main is ok. Voltages on t-con are fine but I'm not sure how to check if picture data is getting through to the panel. I'm going to try my luck with another t-con as they are available cheap. I'm suspecting bad panel but I just don't understand the behaviour of the half-screen test.

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              #7
              Re: CELCUS (VESTEL) CEL-49FHDSB-16/1 - No picture but backlights are on

              Third t-con board fitted and no change. Not too surprising. I guess the panel is bad then.

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